Observation

"Angus, I am glad you are safe." said Jayna

"Me too." said Angus while embracing Jayna.

After having a long night's rest and intimate relations with each other, Angus and Jayna wake up early in the morning and decide to wake Anna before having breakfast. With some spells and hitting her head, they finally woke up the troublemaker.

After having breakfast together, they go towards Jacob's medical room. Unlike Angus and Jayna, who could recover after one night's rest, Jacob and the others need at least a few days to recover completely. 

Therefore, in this weakened state, Jacob could not do much but handle a little paperwork while being medicated. Since he almost overused the mana potion, he couldn't take any typical medication to regenerate and recover his mana faster.

He needs to let his mana recover naturally before making a full recovery. Still, he needs to rest and not overwork himself to fasten his mana regeneration.