The mare wonders if she could possibly use these runes just like Antoine did. It just says the runes need magical energy to activate, and all ponies have that. The difficult part is that unlike her fiance Mulberry has never used magic ever. She knows she has seen Earth Pony mages, so she knows it's possible, she just doesn't know how it works.
She thinks of writing up some runes and trying it out, but then she remembers that some of the notes she found warned against using runes that you don't know. Perhaps there is a place she can find some combination of runes to use?
Mulberry wanders back over to the hole in the room with Hard Tack and looks down into it. Indeed, it appears to be a store room.
On the shelves she sees more cans of food, as well as stacks of flour. Tar and pitch, Paper and quills, ink, firewood, jugs and pottery, and other various sundries and knick-knacks.
She notices there is a door here as well, and based on it's position, it probably leads to the store's front.