Yes, IF is defined as the NP for an effort divided by your FTP. WKO+ only uses the current value of FTP entered in the dialog box on the Athlete Home Page. If you've underestimated your FTP and entered a lower number then your IF will be high and TSS will be very high as TSS is proportional to IF^2.
So if your actual FTP is 300 watts but you've entered it as 280 watts and you do a workout with an NP say 250 watts for an hour:
- your actual IF is .83 and your TSS should be 69
- with the lower FTP entered your IF will report as .89 and you'll record ~ 80 TSS
-Dave