One bag of something (non-standard) refers to a huge amount of something, or a whole heap/lot of something in the Jamaican dialect. It's use is not just limited to things. It can be used with people or even animals.
In colloquial speech the word of is elided and becomes identical to 'a/ah.
One bag of ants outside under the bench.
One bag of unknown numbers keep calling me.
One bag of hungry-belly pickneys live over Miss Janey yard.
When you fit all your groceries in one bag.
I one-bagged all my groceries