It depends on the timeframe selected in the Time Frame Selector. The granularity is set as follows: 1 min for last 30 minutes, 3 min for last 6 hours, etc .
more information on this can be found here: https://www.dynatrace.com/support/help/how-to-use-dynatrace/data-privacy-and-security/data-privacy/d...
Between 30 minutes and 14 days the resolution scales. That three minutes will become five minutes at another milestone and on and on. It's not written down exactly but you can see when you change the time selector and hover over the load graph what the new granularity is.