I recently applied to the University of X for my PhD. One of the potential supervisors (that I mentioned in my SOP), reached out to me with a preliminary round of questions about my research interests and why I want to work with him. After I replied to those, he has sent me the following questions with one of his students in CC.

I am from an electrical engineering background and my research interests lie in the field of Optimization, Data Science, Designing Statistical Models and Machine Learning. I have done a fair bit of coding for some very basic side projects on those topics. But, I lack a proper math background as the professor asks for in this email. In this context, what is the best way to portray this shortfall so that he doesn't lose interest in me? I know it is a bit of a subjective and broad question. But, I am rather confused on this matter. Any and all suggestions would be much appreciated.

TIA

SS of the email I got from the PI