Destiny of the Sands Part 3 boon Question

[Tarma]

This question revolves around the chronicle sheet from Destiny of the Sands Part 3. Super Spoilers ahead.

The chronicle sheet in question:

The boon for Destiny part 3 says that you can turn a feat that you have into a mythic feat for 1 round, as you have used a mythic surge. But a lot of feats use your Mythic Tier to have different bonuses as well. What is the Mythic Tier that is used for the boon?

I've searched on the forums, but I haven't been able to find anything on this boon.