The bug tracker has a field for "size", which is intended to represent how long it will take to implement the feature described (or fix the bug described). Keep the following guidelines in mind while editing that field:

large

a long, multi-day programming project --- work on this should probably live on a branch

medium

a solid several hours or evening of work

small

maybe an hour or two, but it should be fairly straightforward

tiny

a few minutes; probably doable by setting an appropriate config option, copying a chunk of pre-written code, or adding a line or two in the right place