From documentation:

nice - run a program with modified scheduling priority

The flags:

-n, --adjustment=N

The command goes like:

nice -n 19 dms run --session

This starts my DMS shell in least priority. It just means Linux will give any process higher priority. In consequence maybe it will update less since it’s my bar.

Values of n:

-20 (most favorable to the process) to 19 (least favorable to the process).