Effective Use of a Protagonist
A student would gain maximum merit points with minimum effort if they could chain the low-level missions together. Eren was aiming to do exactly that.
Generally, the low-level missions would be released every day and get refreshed within a week. That meant there were around seven sets of missions for each day of the week. Each type would be released on that specific day and would be available for the next week after someone had claimed them.
But that also meant students would need to wait for a day or in the worst case an entire week to claim these low-level missions if someone pulls a fast one on them and takes all such missions from a particular set for themselves. Eren was going to claim all these low-risk-high-return missions in one go so that he could earn maximum merit points during this week.