User blog comment:MachineGunSuper/My axiom about the biggest number/@comment-80.98.179.160-20171218203046/@comment-30754445-20171219143614

Well, n ₵'s is rough equivalent to n tetrations which give you (roughly) 10↑↑↑n (with 3 arrows).

Whether or not this is "fast growing" depends on context. Compared to what the average layman calls "large numbers" (like the googolplex), even 3 arrows are stupendously big.

But compared to Graham's Number, its tiny.

You can use this scale (which is an extension of the usual "classes" of numbers you already know) to place all these functions:

x₵y will usually be class 6.

x₵₵₵₵...₵₵₵₵y with n ₵'s will usually be class 8

and your q125 is class 9. My own iterated version (qq q ) is also class 9

As you probably see, it gets more and more difficult to progress through the classes. And for reference, Graham's Number is class 13, your "Graham Graham" is class 14, and TREE(3) is somewhere around class 120 (!).