Medic feat: does it only work for one hit die, or more?

Question

The Medic feat (from Unearthed Arcana: Feats for Skills) has the following description:

During a short rest, you can clean and bind the wounds of up to six willing beasts and humanoids. Make a DC 15 Wisdom (Medicine) check for each creature. On a success, if a creature spends a Hit Die during this rest, that creature can forgo the roll and instead regain the maximum number of hit points the die can restore. A creature can do so only once per rest, regardless of how many Hit Dice it spends.

Can a creature benefit from this feat for multiple hit dice?

Example: I short rest, and someone with the Medic feat binds my wounds. I use 3 Hit Die of d10 (Fighter).

Do I recover 30 HP, or only 10+2d10?

Answer 1

You heal 10+2d10.

Part of your emphasis on the feat description: "...if a creature spends a Hit Die during this rest..." Singular.

Last sentence of the Medic feature:

A creature can do so only once per rest, regardless of how many Hit Dice it spends.

RAW on using hit dice to heal after a short rest (emphasis mine):

(PHB Chapter 8, Page 186)

A character can spend one or more Hit Dice at the end of a short rest, up to the character’s maximum number of Hit Dice, which is equal to the character’s level. 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.

This means the dice are rolled one by one and you decide to continue or not after seeing the first roll.

Also note that the Medic feature is used instead of rolling the die.

... that creature can forgo the roll and instead regain the maximum number of hit points the die can restore.

Note: If you are unsure whether the Medic adds your CON modifier to healing like i am check this question.

Answer 2

10+2d10

This line reveals how it works (recall that the feature references a single die):

A creature can do so only once per rest, regardless of how many Hit Dice it spends.

You will gain the maximum roll from only 1 die meaning that you must roll the other two.

It is worth noting that you don't restore 3d10 without the medic feat but instead restore 1d10 + 1d10 + 1d10. This is relevant since you can choose to expend another hit die after the rolls (under Short Rest in the Player's Handbook):

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.