I'm facing a file with the records from a game (all that happened in the game: kicks, center bounces, handballs, etc.) and I don't understand the difference between "loose ball get" and "loose ball get crumb" (same for "hard ball get" and "hard ball get crumb"). I am not sure whether this is usual terminology or not.
As @philip-kendall points out in the comments, the answer is in the Wikipedia article Glossary of Australian rules football:
Loose ball get: a disputed ball at ground level not under direct physical pressure that results in an opportunity to record a legal disposal. Counted as a contested possession.
Crumb: a ball that spills loose from a contest. [...]
So basically the difference is where the handball comes from. For example, if it comes from an ineffective kick it would be a loose/hard ball get. If it comes from a contest where none of the players got it, it would be a loose/hard ball get crumb.