It is a property of the number of files only.
Use rclone size /home to tell you how many files there are.
As a rule of thumb expect about 1k memory usage per file very approximately.
If you want to find out more exactly, then download the latest beta and run rclone test memory
Eg
$ rclone -l test memory ~
2021/02/15 18:06:10 NOTICE: 1175288 objects took 328368648 bytes, 279.4 bytes/object
2021/02/15 18:06:10 NOTICE: System memory changed from 75908104 to 928049864 bytes a change of 852141760 bytes
You'll need to run it once for the source and once for the destination to get the full picture.