improvement value question

[Jim Fang]

Hi, I bought a rental property in 2018 and am working on tax return with turbotax now. Need to find land value and improvement value and numbers on county assessor's website are shown below. Why there is about ten fold difference between market value and assessed value? The latter is even smaller than land value? I bought it @ $375K+closing cost+repair cost.  the dwelling number on the insurance is 387k. How to calculate improvement value? Thanks a lot.