How to input Undetermined term transactions for noncovered tax lot as GBTC investment expense not regular sales in Turbotax?

I import 1099-B from TDAmeritrade into Turbotax.  The transactions for GBTC are some proceeds for investment expense (Principle payment). But Turbotax take it as gain instead of investment expense since the sale quantity is 0, data acquired is n/a, and cost basis is "...".
What should I do to make Turbotax treat theses proceeds values as investment cost not sales' gain?
Thank you