Constant increase in RAM usage - Synology DS220+, DSM 7.x, Docker

I run 2 nodes on 2 Synology NAS, DS216+ 1GB and DS220+ 6GB.
DS216+ has been running great, with 1.4/7TB occupied.
DS220+ is new, under a month old, with 9GB/14TB occupied.
Both run DSM 7.x and Docker up-to-date, identicaly configured, only 1 HDD per machine. The only difference, besides the hardware specs, is that DS216+ has the volume configured as RAID SHR and DS220+ has RAID Basic. Both use ext4.
The problem: The DS216+ shows correct RAM usage, 3xx MB for the storagenode, but the DS220+ shows continuously increasing RAM usage. Yesterday was 1.46GB, and now is 2.9GB.
I restarted both in the same time, one day after the autoupdate to 1.47.3.
What’s with that huge memory usage? Why there are 2 contradictory RAM values in Docker?
What happens if it fills the entire RAM?

ds220p 5

Please take a look