Does 244HP ensure max recovery from Poison Heal?
To ensure maximum recovery from Poison Heal, Gliscor should have its HP divisible by 8 (since Poison Heal recovers 1/8th of your MAX hp per turn).
Looking at the highest possible number divisible by 8, you get 176 (the next value would be 184, however Gliscor's max possible HP is only 182 at level 50).
And since you're using Substitute in the set, ideally you would also want your HP to be divisible by 4, add 1 (the reason for this is, say if your max HP is 101, it costs you 25 HP to make 1 sub, so with 100 HP you can only make 3 subs but with 101 it gives you 4 full subs).
Therefore, the HP you want to aim for on Gliscor looking to max recovery WHILE using sub is 177 (or 212 EVs in HP).
The beauty with HP number is that it's also divisible by 16 (or more commonly known as 16n+1, meaning you'll be minimizing residual damage from weather such as Hail which deals 1/16th of your MAX hp per turn).
So with 177 HP, it will cost you 44 HP to make 1 sub, while you get 22 HP back from Poison Heal.
But because of how rounding down works in the game, 244 EVs in HP gives you 181 HP, meaning it will now cost 45 HP to make 1 sub, while you still get 22 HP back from Poison Heal, so you're basically losing 1 HP every cycle in the long run.
With that said, it won't really matter in the end (for most matches both HP spreads will suffice).