In the ClrHome.org z80 opcode table, it says that JP uses 10 cycles and JR uses 12/7 cycles. Does 12/7 cycles mean that it takes 12 on a jump and 7 on a pass, or the other way around?

It takes 12 cycles if it needs to jump and 7 if it doesn't need to jump.

https://tutorials.eeems.ca/ASMin28Days/ref/z80is.html

Yeah, on the z80 "jp" is generally faster if you're making the jump but one byte larger, "jr" is typically slower (except when using the conditional version where the condition is false/no jump is taken) but one byte smaller. It's a convoluted case of the classic "size vs. speed".

Like Hot_Dog posted, i like the formatting of the ASM in 28 Days instruction set and that's my go-to reference when i need to confirm how many T-states an instruction takes.