I wonder what percentage of their dilithium they just gave away, without realising just how valuable it now is, and what that does to the ship's operational time.
Dilithium's a little odd in that it's not actually a fuel - Federation starships are fuelled by antimatter. The dilithium is what allows the matter and antimatter to come together in a controlled fashion inside the warp core, emitting their energy into the warp nacelles instead of in a random direction. However, dilithium crystals do break down gradually when in use, and as of Discovery's origin time they hadn't yet developed the technology to recrystalise spent crystals (introduced as a plot point in Star Trek IV, and built into the warp drive as standard by the TNG era), so Discovery is actually thirstier in terms of dilithium consumption than more modern vessels.
On the other hand, they only really need to use dilithium when they're travelling at warp speeds, so this could make their Spore drive even more valuable to them than it already was.