Georgia teachers retirement adjustment.

What number do I use on my Georgia Tax return when it asks 

Contributions to your teacher's retirement paid between July 1, 1987 and December 31, 1989 may have been taxed by the state of Georgia. If so, a portion of your retirement received during 2017 may not  be taxable.

Do I put the entire Taxable amount?  or do I subtract the taxable amount from the gross distribution?