Not sure where you got your numbers. GAAP Net revenue for FY25 was $7.5B.

https://ir.ea.com/press-releases/press-release-details/2025/Electronic-Arts-Reports-Q1-FY26-Results/default.aspx#%3A%7E%3Atext=In+fiscal+year+2025%2C+EA%2Crevenue+of+approximately+%247.5+billion.

Your highest rank is based on your level. Technically this would give you a single rank four slot at level 9, a rank 5 slot at level 11, etc. without taking the expert or master spellcasting feats.

Yes, if you had spells from your sorcerer that overlapped with the mystery’s spells, you could cast them using the extra slot without taking the basic spellcasting feat.

True. That was probably a bad example. But if you picked up basic oracle spellcasting, that would let you cast the spells granted by your mystery.

So you’d get an extra slot at your highest rank. For basic spell casting, this would be one rank 3 slot at level 8, so with gift of power you’d have two slots, one that would only let you cast spells granted by your mystery.

The first part of the feat gives you an extra spell slot of your highest spell rank, but that slot can only be used to cast spells granted from your mystery. For an Oracle dedication, you’d need to take additional archetype feats to get access to Oracle mystery spells, e.g., https://2e.aonprd.com/Feats.aspx?ID=6220

If you also happen to pick up divine access or mysterious repertoire, then you can use this extra slot to cast spells granted by those feats as well.

https://2e.aonprd.com/Feats.aspx?ID=6064

From reading this, it doesn’t look like it would affect your other spells at all:

Your mystery grants you additional magic. You have an extra spell slot of your highest rank, which you can use only to cast one of your mystery's granted spells, heightened to this rank.

Special If you have the divine access class feature or Mysterious Repertoire feat, you can cast spells that you learned from those abilities using the additional spell slot from Gifted Power.

I’d highly recommend joining the Foundry discord if you haven’t already. It’s very active, has channels for anything and everything, and people are generally helpful.

https://discord.gg/foundryvtt

Their GitHub page might also help with technical details.

https://github.com/foundryvtt

What about the Mach 20?