Heart Rate Graph Misses Max

I have a desk job, and my heart rate hovers around 50 to 60 bpm most of the day. Today I carried a heavy box up a flight of stairs and checked my HR at the top and it was 131.

An hour later I looked at the graph, and the max is 110.

For the graph itself it has to average some readings to get 4 hours of bars across the screen, but is the min/max also averaged? I guess they might do that to prevent one or two erroneous readings from wiping out the real max.

I wasn't at 131 for very long but I'm surprised that doesn't show up on the graph as the max reading.