Hey Sargon!
Thank you for the kind words!
You can change the value by editing this file: <game folder>i\data\MMH55-Index.pak\GameMechanics\RefTables\WarMachines.xdb.
If you have no experience with .pak files before, you can read about how to modify them here.Find an item with id WAR_MACHINE_FIRST_AID_TENT
and change the value from 3 to whatever you want!
I have no experience with this format, but thanks for the link - I'll figure it out and I think I'll do everything right.
Have a good mood and fruitful work... and modding too!

Added after 23 hours 20 minutes
Dredknight - thank you again, everything went successfully. The tent now has its 10 shots. 👍