To clarify, since you have already entered a 1099-int to show a distribution of a portion of the trust interest income going to the decedent final return, then you can do either way. If the software will allow you to enter the full amount and then subtract out the amount paid to the decedent as "decedent final return" portion, it makes for a cleaner return for IRS to follow.
TurboTax may not allow you to enter a - entry for the decedent final return share, so if it won't, then you can just enter the portion that belongs on the trust return and name it with detail, like "Bank Interest Less Decedent Final Return portion" and then enter the remaining amount that stays on the trust return.
The Trust return should show the amount of interest income carrying into the trust and the decedent final return should show the amount carrying to the Decedent Final Return per the following:
IRS Publication 559
