RAM usage - Edge and Firefox browsers on Linux Mint

I've installed 'Graphical Hardware monitor' to show RAM, Disk read and Disk write on the panel of the old Macbook Pro running Linux, which has only 4 GB of RAM including VRAM. Curious to see RAM usage, tried opening Gmail + GDrive + a spreadsheet on Firefox and Edge browsers separately. With Firefox, total RAM used was 1.92 GB. With Edge, it was 1.63 GB. So, Firefox was using around 300 MB more than Edge in this (not too rigourous) test.