Applying GST on imports and customs

I am following the method for setting a GST amount on imports via adding it to a transaction with GST of the original value and a N-T coded reverse transaction.

However I am trying to do this in the Bank Transactions Allocate funds screen and it is not recognising the value of the GST in the Balance, so does not allow me to save my transaction as it thinks this is an unbalanced allocation. How should I do this?

EDIT

Actually fixed it, the reverse N-T entry should be 90% of the GST entry.