What does the term “Conformity Subtraction” refer to in the list of income and deduction amounts to be allocated in a state return for a part year resident?

I moved from VA to MA during 2024 and, for my VA state return, TurboTax is asking me to allocate various Federal income and deduction amounts to VA, one of which is designated as the “Conformity Subtraction”. I don’t know what that reference is to or where TurboTax generated that amount from, so I don’t know what methodology I should use to determine the portion to be allocated to VA.