There are many ways to set up milestones. For more options, see the full list here. This article goes over the single hour requirement, how it'll look on a report, common examples, and how to configure it.
This is the simplest milestone configuration you can set up, which requires ONE set goal for a specified time frame. Some examples of this include:
To configure single requirement milestones, go to your Organizer Dashboard
Click on the Settings tab, then click on Milestones
Click on Single Hourly Requirement radio button
Insert an integer for how many hours you will require
Select a time period
You can also set up a custom time frame. For example: if you want to set up hours for a school year that runs from September to June, you would select Every 1 Year starting on 9/1/2018.
Milestones automatically reset after each specified timeframe, until changes are applied or turned off.