Axis labels in monitor results are off

I have the following setup: hourly monitor, “monitory summary”, “all requests”, “sum”.
When I hover a certain result, the overlay says e.g. 23.76 seconds, which matches the summed up test results below, but according to the axis on the left it should be around 18.53 seconds.
Am I doing something wrong here? Don’t understand how this axis works :confused: