A bronze medal is worth +2, silver +4 and gold +6. You never type a number, so a bonus always sits in proportion to the buttons. These are the companion's medals, and they are not the same as the medals a teacher gives at school, which are smaller.
Use it for the moment the list does not cover: the hard thing they kept going at, the kindness nobody asked for. A bonus adds to every prize, the same way a button does. Like any tap, it can be undone for 5 minutes; after that it is theirs.