How in HECK to you figure HP on a B&S engine?

Took me too long to find this..

first 2 digits = DISPLACEMENT
3rd digit = ENGINE SERIES

rest is just BS like bearing and starter type (prob the same for all lawnmowers)

Briggs official website breaks it down here:
https://www.briggsandstratton.com/c.../en_us/Files/Numerical_Designation_System.pdf