At the end of a Short Rest, you could spend any number of Healing Surges and, for each one, recover one quarter of your maximum HP. And generally, most classes had enough Healing Surges to recover their full complement of HP two to three times over.
What do you recover during a short rest?
Short Rest The character regains Hit Points equal to the total. The player can decide to spend an additional Hit Die after each roll. A character regains some spent Hit Dice upon finishing a Long Rest, as explained below.
When do you get the hit die and Constitution modifier?
Each level, you get Hit Die + Constitution modifier additional Maximum HP. You always take the maximum of the Hit Die at 1st level; afterward, you may roll the Hit Die or take its average rounded up. Therefore, with a 1d10 Hit Die and +3 Constitution modifier, assuming you take 6 each time instead of rolling:
Is the con modifier added every time you level?
tl;dr Short answer is the con mod is added each time you level, but should it change at any time your hitpoints gained previously need to be recalculated with the updated constitution modifier. More information about hitpoints as you level can be found on page 15 of the Players Handbook.
What happens when you spend a hit Die?
For each Hit Die spent in this way, the player rolls the die and adds the character’s Constitution modifier to it. The character regains hit points equal to the total. The player can decide to spend an additional Hit Die after each roll.
When do I add a con modifier to my hp?
For the sake of this calculation if you have the tough feat add an additional +2 to your con modifier. Because changes to constitution modifier are applied retroactively one formula can calculate your total hitpoints at any level or change in constitution modifier. Example: A level 20 Barbarian, hit dice size 12, constitution modifier +6.
