[AkaInuHime]

Dragging high-quality bandages to your character portrait or map sprite, from either your inventory or hotbar, consumes and applies two at once. For me, this happens about 80% of the time when trying to use them.

[Neus]

This has been corrected in 2.99.

In the meantime, this only occurs if you have the inventory open. Dragging and dropping from your utility belt while the inventory is closed will consume just 1 as intended.