Minimum entries per scout
Once you're written all the questions for a diary study style mission, you'll need to decide how many times you'd like scouts to go through and answer all those questions. Each time scouts answer those questions, they'll submit an entry.
Telling scouts the number of entries they need to submit in order to complete your mission gives them a good idea of how much you're officially asking from them, but they can always submit more!
If you're asking scouts to submit more than 1 entry, it needs to make sense for scouts to answer all the questions in your mission multiple times.
Take a look at the defining specs article for more details.