My postgresql are using

602Mi

but in frontend ui I see the Actual Size is

2.26 Gi

I have 2 snapshots • Size: 531Mi • Size: 907Mi and VolumeHead is 883Mi why snapshots takes so much memory when the total memory of postgresql (602) is less than second snapshot?

You can check this for more details: https://longhorn.io/docs/1.2.4/volumes-and-nodes/volume-size/#volume-actual-size