From: United States
"Numple" makes it sound like it should be pronounced NUM-pull which is not quite right. The katakana is na-n-pu-re, and should be pronounced "nan-prey" (the u is a whispered vowel) which is an abbreviation of "nanbaa pureisu" (Number Place). In Japanese, this kind of abbreviating is quite common, such as seeing Pic-a-piz puzzles abbreviated as "iraroji" (Illustrated Logic).
Transliterating any kind of non-romanized language into romanized characters is always tricky and there are sometimes multiple ways of spelling the same thing (such as the Japanese R which is really an R/L sound).