I'm on 1.18.2 and using this mod for my own modpack. Sometimes I commit the big dum dum.
I often have to redo things because half an hour doesn't cover what I did.

I want to reduce it to 15 or even 10 minutes but I don't understand how to exactly write that in the config. I understand the rest, can configure that but the time format kind of confuses me too much that I feel confident to touch it.
What would I need to write for such a thing (specifically set it to every 10 min)?

Also sorry I post in here, I had no clue where to ask for help.

Until somebody lets you know, and if your pack is Fabric, I would suggest using Textile Backup: https://modrinth.com/mod/textile_backup
Also has a very good wiki: https://github.com/Szum123321/textile_backup/wiki
Its backup frequency is in seconds (Default 3600)

There is a link in the configuration file to a website which allows you to generate the string needed, it is standard cron notation. If you visit the link it will give you a nice gui to build how often you want backups to happen.