Calories chart sets axis units to hh:mm?

I added a chart to my Fitness page with 2 plots - Calories (Weekly Total) & Distance (Weekly Total). But the axis units for the calories side are in hh:mm instead of kcals (top chart in screenshot)

I also plotted calories alone on its own chart - here the units on the axis are correct (bottom chart in screenshot)

Looks like it may be a bug?