The gist of this formula is that it figures out bundles needed, given items needed, and a specific bundle size.
For example, if you need 6 items, and the bundle size is 2, you'll need 3 bundles. If you need 3 items, and the bundle size is 5, you'll need 1 bundle (and you'll end up with 2 extra items).
First, we use the CEILING function get an item count needed, taking into account the bundle size.
The CEILING function is fully automatic. It will round a number up until it reaches a number evenly divisible by a given multiple (bundle in this case).
Finally, we divide the number provided by CEILING by the orignal bundle size.
The result is the the total number of bundles required.