What does Heart Rate HD PPG Raw Data means？

[Yaosmart]

I have a Ticwatch 3 Pro. And I want to get the raw data of the ppg, including the value from red/green/IR lights value.When I list the sensors, I find an item, " / Name: Heart Rate HD PPG Raw Data /Type_String: android.sensor.mobvoi_hd_ppg_raw /Type_number: 69642". And I try to listen to the PPG sensor on 69642.

The values I got like that:
PPG_HD: -16616.0 -4525.0 -3805.0 90930153387943
However , I do not know what the [-16616.0, -4525.0, -3805.0] means.