Spending multiple strings

We had a rule question come up during the game:

Can you spend multiple strings on a roll to increase it by that number?

I was thinking you could because the closest analogue I could think of was spending Trust in Mountain Witch, but I didn't know for sure.

The book doesn't seem to give a clear answer on my last read through.

You can't spend multiple Strings to trigger the same effect multiple times, in any given moment. You can't offer someone 3 XP to do something, nor add +3 to a roll.

You can spend multiple Strings to trigger the same effect multiple times over the course of a scene, though. You could offer someone 1 XP to do something, and then follow up with offering someone 1 XP to do something else.