The powdered compound also stores well, which is great for a DIYer. After a month or two you will find a half-used bucket of premix will be moldy or dried out... yuck...

This sort of thing - the number is how long it takes for initial set up (in minutes). You can get 5, 20, 45, 90. The 5 is really only for very quick small repairs for someone that needs to be in and out of a job quickly. The time varies with temperature and humidity. https://www.homedepot.com/p/USG-Sheetrock-Brand-18-lb-Easy-Sand-90-Lightweight-Setting-Type-Joint-Compound-384211/100321611