That is an interesting question about number of justices on SCOTUS - and so I did a shallow belly flop swan dive into the shallow pool:
https://www.britannica.com/story/why-are-there-nine-justices-on-the-u.s.-supreme-court
Interesting article at link, but this is the relevant excerpt:
“...Basically, the U.S. Constitution grants Congress the power to determine how many justices sit on SCOTUS. This number has ranged between 5 and 10, but since 1869 the number has been set at 9. ...”
Tummy rub. Brave TEXOKIE.