I have shared som exercises to Facebook, but when these are opened, the "% of Max" and "% Avg HR" fields are wrongly calculated.
E.g. my max HR (in profile) is really 204, but a value of 188 will cause Max HR to display as 102% of Max. If I log in as myself and display the same activity, the Max HR is correctly calculated (92%).
I guess this has something to do with a "no logged in page" not able to retrieve the max hr of a user to calculate this, but I guess the option to show this should not be availble then.