I didn’t really understand your question.
each active user receives its own TFI.
In one TRX of a cell, for example, there is, let’s say, 30 users that are using DL + UL TBF. Each of them have its own TFI for UL and also a TFI in DL. They may or may not be the same. TFI is just the identifier of a TBF.
In another TRX of the cell, there could be, let’s say, 25 users. Each of them would have their own TFI (or couple of TFI, 1 UL, 1 DL).