Thank you for using "number of" instead of incorrectly using amount as is the current trend.
I wouldn't worry about it much but "amount" should be used with uncountable nouns, "number" with countable nouns
Ah thanks!
It's kinda weird to me, but I guess it makes sense in the context of English having distinct words for countable and not
Amount is for things you cannot count. For example, an amount of water. If you can count it, use number of.
HOWEVER, English is not a dead language, so the definition of amount may just be changing.