Deductions & credits

how do you differentiate when there's 15 houses?   i did this and the IRS added the 1099S that the title company sent for individual houses that were grouped together on my schedule C, now i'm fighting them and having to show them my numbers are in there.   So essentially, I am getting hit with a $377k bill from 2016.  this is not accurate.  So now I'm trying to figure out how to fix the stuff i was lead to do on my schedule C.