comparison previous period changes

Hi,

I have a dashboard in Google Looker Studio. In this dashboard is Google Analytics 4 connected to a score card, visitors. The comparison is set to previous period, so it is in comparison with 31 march t/m 30 april. When I switch in the date range to April and then back to May, the comparison is changed.

Nothing has changed in the settings. Can somebody help me, why this occurs?

Zoé Gerritsen