When you create a new custom table. lets call it projects, you can attach multiple activities to each project record.
This allows you to schedule multiple activities which appear on your calendar but are attached to a specific project.
You can also calculate values from all the attached activities up into the project table.
By default there are 16 fields which calculate up: these fields are named: "Activities Count" "Activities Count Open" "Activities Count Closed" "Activities Count Percentage"
You may want to break each activity into multiple fields. Lets say you schedule an activity which is from 9-5. By default the "Activities Duration" field will total this as 8 hours. But the technician was traveling two of those hours and another 2 hours was completed on warranty work. leaving a total of 4 actual hours billable.
To total these hourly bucket you need to create these fields in both tables. The Activity table and the Project table. These fields need to be the same type such as numeric or currency.