
Why on earth does the diagram have 3 lines between 40 and 70?? So I have to calculate 40, 47.5, 55, 62.5, 70???
It appears to me that the watch automatically sets the number of the top and bottom lines to whatever multiples of 10 are necessary to contain The range daily RHR values have been calculated for the prior 7 days and that range is always divided into quadrants by the three graph lines. Right now my top and bottom lines are 50 and 40; a couple of days ago they were 50 and 30. I don't find it very difficult to understand the gist of the RHR trend from the graph, but if you need exact numbers for prior days, you can get them on the Connect app.
p = (high - low) / 10
if (p mod 2) == 0 then num_lines = 3 // covers p mod 4 == 0
if (p mod 3) == 0 then num_lines = 2
if (p mod 5) == 0 then num_lines = 4 // not very likely, but hey ...
Garmin plotting (be it on the watch, GC or GCM) is absolute crap! There too many inconsistencies/errors/bugs that it doesn't make sense losing sleep over it.
It's hard to swallow but a $500+ Garmin is the best we have as Suunto and Polar are even worse ...