When determining if it is reasonable if the heap is increasing or not, our rule (IncreasingLiveSetRule, if it triggers) say that it can be an artifact of a short recording. However, if you have a JVM running for a week and grab a flight recording of 2 minutes after that week, you should not expect the heap to grow constantly.
If you go the the JVM Internals page and look at the JVM Start Time, you don't see the start time of the flight recording at the same time. Was this JVM started long before the recording or not? Tricky to say without switching between pages.
I suggest some information about when the recording was started in this page. One alternative is to have a tooltip over the start time of the JVM and relate it to the start time of the flight recording. It could say something like "The JVM was started 2 hours 3 minutes 4,567 seconds before this flight recording", or even just the start time of this flight recording. (Perhaps its better to not use a tooltip: whatever, the info would be useful).