Step 1) Ask ChatGPT what the heck this is-

what is this? "NT Ext Eq Mkt Indx Fd DC Lendin..."

• NT Ext Eq Mkt Indx Fd: This stands for "Northern Trust Extended Equity Market Index Fund." Northern Trust is a financial services company that offers various investment products. An "Extended Equity Market Index Fund" typically aims to replicate the performance of a specific stock market index, which might include a broad range of equities outside the main indices like the S&P 500.
• DC: This likely stands for "Defined Contribution," indicating that this fund is part of a defined contribution retirement plan, such as a 401(k).
• Lendin: This is probably short for "Lending," referring to securities lending. This means the fund may lend out the securities it holds to other financial institutions in exchange for a fee, which can generate additional income for the fund.

So, it's essentially a retirement fund invested in a diversified mix of equities, potentially including mid-cap or small-cap stocks, with an option for securities lending to enhance returns.

Step 2) Let's see what we can find about it- Oh look a report:
https://workplace.schwab.com/resource/ntc-extended-equity-market-index-fund-lending
"The primary objective of the Northern Trust Collective Extended Equity Market Index Fund - Lending is to approximate the risk and return characteristics of the Dow Jones U.S. Completion Total Stock Market Index. This Index is commonly used to represent the small and mid cap segments of the U.S. market.
Investment Approach To achieve its objective, the Fund employs a replication technique which generally seeks to hold each index constituent in its proportional index weight. The Fund may make limited use of futures and/or options for the purpose of maintaining equity exposure. This Fund may participate in securities lending."

"FOR ONE ON-ON-ONE USE with Institutional Investors/Financial Professionals Only. Not For Retail Use. This information is intended for one-on-one use with current or prospective clients of Northern Trust Investments, Inc. This information is confidential and may not be duplicated in any form or disseminated without prior consent. Northern Trust and its affiliates may have positions in and may effect transactions in the markets, contracts and related investments different than described in this information. This information is obtained from sources believed to be reliable, and its accuracy and completeness are not guaranteed. Information does not constitute a recommendation of any investment strategy, is not intended as investment advice and does not take into account all the circumstances of each investor. This factsheet is provided for informational purposes only and is not intended to be, and should not be construed as, an offer, solicitation or recommendation with respect to any transaction and should not be treated as legal advice, investment advice or tax advice. Recipients should not rely upon this information as a substitute for obtaining specific legal or tax advice from their own professional legal or tax advisors. Information is subject to change based on market or other conditions. The fund is a collective trust fund for which Northern Trust Investments, Inc. serves as trustee. The fund is not a mutual fund and is privately offered. Prospectuses are not required and fees and expenses are not available in local publications."

....This could be pretty interesting if real.

Step3) See if I can find a list of stonks owned by northern trust, look at midcaps because this is a midcap fund -

https://fintel.io/i/northern-trust

As I start pulling up these midcaps, I see quite a few other stocks with the same issue.

https://preview.redd.it/0d3jk2vulmmd1.png?width=1110&format=png&auto=webp&s=04ab832c910eadb4823b0c047cfe86658a435009

https://preview.redd.it/ntlazd01mmmd1.png?width=1132&format=png&auto=webp&s=445e00114824fe603c2a3b0510ef39370d90b4a0

https://preview.redd.it/andc9f7kmmmd1.png?width=1115&format=png&auto=webp&s=f4dec4e135547109e863403ffdf39c6366036fc2

TREX float is only 109.7m shares. MORN's is 36m. PJT is larger, but the ownership size is still disproportionately large.

I found several other companies with the same issue. Just glancing through them... if these numbers were accurate, this fund would be worth several trillion dollars. It is not, according to that report I think this fund manages about $12bn. According to these numbers, it owns more than $12bn of Yelp alone.

CONCLUSION: The Northern Trust Extended Equity Market Index Fund is very likely having a reporting issue, this is not specific to GME.