Deductions & credits

Thanks. 

In Turbo tax, when I say "yes" to a previous sale, it asks for the "gain from the prior sale." Our 2119 from that year states the gain was $30K. However, that amount does not take into account the amount that we had invested into the property. So I am wondering if I determine the "gain from prior sale" based on what is reported on the 2119, or can I now use what was invested in the property back then (I kept the records) to determine the actual gain?

Thanks.