When adding monitor groups, there is a field named Monitor count threshold to decide the monitor group's status that you can base the group status on down monitors but that depends on a static count of monitors in the group. It would be nice to make that allow percentage as well.
The benefit of this is because sometimes monitor groups can grow and the set number of monitors to mark the group as down may change and it requires a manual update to happen. Percentages will always use the total number of monitors in the group and calculate the amount of down monitors needed to match the % and determine if the group is down or not.
For example, lets say you start with a group of 5 monitors and you set this to 3 to mark the group as down. Next quarter you add 6 more monitors to make it 11 monitors total. You now need to go back into that group and adjust the down mark from 3 to lets say 7. If we use percentage instead we could say 75% and it would just calculate the number for you.