The game uses the following measures:

Millions
Billions
Trillions
quadrillions
Quintillions
sextillions
Septillions
Octillions
Nonillions
decillions
Undecillions
Duodecillions
Tredecillions

As you see, some of them start with the same letter.

We use "q" for quadrillions, and "Q" for Quintillions.

It is the same with sextillions ("s"), and Septillions ("S").

It happens again with Decillions ("d"), and Duodecillions ("D").