The basic rules dictate that Patching gives an extra card, while playing an Inverter doesn’t. The Really Fast Time Machine (RFTM) lets me play an extra Patch or Inverter, and draw an extra card. So does this mean:

a) If one has the Really Fast Time Machine and uses it to play an Inverter card one can draw an extra card, and if one uses the Really Fast Time Machine to play a patch card, one can draw an extra card.
-or-
b) If one uses the Really Fast Time Machine card to play an Inverter card, one does not draw an extra card, but if one uses the Really Fast
Time Machine card to play a Patch card, one can draw an extra card.

A: Actually, neither of your scenarios is quite correct. Here’s what’s happening:

When you play a Patch, you get an extra card in your hand as a reward for fixing the timeline. Your hand should end up one card larger than it was before you started your turn. This should happen no matter what the circumstances that allowed you to play that patch, whether it was your regular turn, or a patch played using the Really Fast Time Machine (RFTM).

Now, the regular turn action is meant to be a zero-sum equation: you draw one card, and play one card, and your hand will end up the same size as before you drew (unless you patch, in which case it will increase by one). The RFTM lets you play an extra card out of your hand after that. Regardless of what card you played, that would decrease your hand size, and the intention is that it should stay the same, i.e. it should be a second zero-sum play. It’s a little like getting to take a second turn, except you play before you draw, and you are limited to only Inverters or Patches for your second “turn”.

So, if you use your RFTM to play an Inverter, you draw one to replace the Inverter in your hand, so that your hand size does not decrease because of the RFTM.

If you use your RFTM to play a Patch, you draw one to replace the extra card you played out of your hand, to restore it to the correct size, and THEN you draw a second card as your patch-reward card, for fixing the timeline. So your hand size should increase by one because of the repair, as intended.