What does heart rate '-10' mean?

I bought the Samsung smart watches as below.

  1. Samsung Galaxy Active 2 / 2019 / SM-R830 (SM-R830NZKAKOO)
  2. Samsung Galaxy Watch 3 / 2020 / SM-R850 (SM-R830NZDAKOO)

Watch 1 and 2 are both TizenOS ver. 5.5.0.1.
Watch 1 and 2 are both using my same application version. (i.e. same source code)

As shown in the second attached image,
‘Watch2’ recently purchased shows a strange heart rate value.
When wearing a watch and moving, the ‘-10’ value is recorded for the heart rate.
This did not occur in ‘Watch1’ in the same environment except for hardware differences.

Is the heart rate measurement algorithm between the sports type and the classical type different?
Or is there a problem with the watch I bought?

active2_정상HRM
watch3_비정상HRM

In ideal case this issue should not happen. Try to check the issue on the latest software version of the watches. If the issue is specific and consistent then submit a support request