How does Wintertodt damage round?

Wintertodt damage is calculated based on your HP level, your Firemaking level, the number of warm items you have equipped up to 4, and the number of braziers lit up to 3.

For a standard attack, the formula is:

dmg = ((16 - W - 2B) * (HP + 1)) / FM

where W is the number of warm items up to 4, B is the number of braziers lit up to 3, and HP and FM are your HP and Firemaking levels. Best case scenario, this can be simplified to

dmg = (6 * (HP + 1)) / FM

How does this damage number round? Does the game use round, floor, or ceiling? For instance, suppose my hitpoints level is 32 and my firemaking level is 79. The calculated damage is 2.5063. Would this round to 3 damage per hit or 2?

Under the Wintertodt's Attacks section of the Wiki, it lists the formulas you mention, and also states the damage is all rounded down (floor):

The following formulas can be used to determine the amount of damage taken, rounded down

This information was originally sourced from a tweet from Mod Ed.