Was it purchased at a foreclosure auction? If not, and it was either a short sale prior to foreclosure or REO purchased from the lender, the value is cut and dried. The purchase price (inclusive of any debts assumed) is the value. No assessed value adjustment for a good deal. State law.

If it was an actual purchase at the foreclosure auction, it might get a bit more complicated. (Which is my way of saying I have no clue what the law is. I could speculate but hopefully someone that knows can actually chime in.)