Adding this mod to an existing save now that it's updated but it puts me over the tile limit. What tiles does it add? Does the helipad count as more than one tile type?

It's a hardcoded 1 byte tile limit, as to preserve space on saves. You have to remove mods or tiles from other mods if you want to play with more. Or, ask the factorio devs very nicely to add an option for 2, 4 or hell even 8 byte tile limit on saves.

No I get that, I've run into the same issue in the past. I just find it really strange that I would be at exactly 255 tiles without this mod (assuming the helipad only counts as 1 tile ID). Removing mods that add tiles isn't really a possibility as I'm already pretty far into my save and have used many of them along with all the alien biomes terrain on the map.

Really I just wanted confirmation of how many tile IDs this mod uses

require("util")

local heliConcrete = table.deepcopy(data.raw.tile["refined-concrete"])
heliConcrete.name = "heli-pad-concrete"
heliConcrete.minable = {hardness = 0.2, mining_time = 0.5}

data:extend({heliConcrete})
Thats the helipad code.
To get the tile count do (in control.lua of a mod or scenario):
local count = 0 for _, _ in pairs(data.raw.tile) do count = count + 1 end game.print(count)

I tried the command but it gave an error "attempt to index global 'data' (a nil value)"

Well then try it in a control.lua like in a scenario or mod.

I'm not sure what you mean, I'm not a coder. I tried running it in sandbox and also tried adding that line to the end of the control.lua file in a scenario but it still didn't work.

/c game.print(#game.tile_prototypes)