There’s no such thing as doing a little bit of time intelligence. You either are or you’re not - and in this case you clearly are, so you should use a dedicated date table connected to your data model.
Then you’ll just need to write a basic RANKX measure ranking incidents by date, decide how you want to handle ties and have the measure return the ranking if less than or equal to 5, blank otherwise.
Hey @Ikay it will be really easy to add a Date Table into this report and get this working. Grab the eDNA Data Table, put it into your report and follow BrianJ’s RANKX suggestion, you’ll be good to go.