Weird! I must have said something wrong? Let me show you how I got this hit/double at Kat TC=-3.7 for the hand 9v6.
The Wizard’s basic strategy for an 8-deck SP21 shoe for 9v6 is double. We consider this particular situation only, player (4,5)v6. The Kat HiLo TC calculation is:

TC=(-32+3)/[(384-3)/48]=-3.7.

This is the critical hit/double point because I’ve checked it. That means the hit/double index is TC=-3.7. Is there a problem with this calculation?