How do I preform a certain action a certain amount of times in 1 second evenly split out?

Let's say I want to preform an action 15 times in a second. I want to make sure the action was preformed exactly 15 times in exactly 1 second. How do I do that?

I've tried this:

local oldTime = os.time();
local amount = 15;
local iteration = 1;

while os.time() == oldTime do
	wait(1 / amount);
	iteration += 1;
end;

print(iteration)

If you don't know what it does, there is a loop that only lasts for 1 second, and it waits 1 15th of a second and adds 1 to a variable until a second has passed

But when I print the variable that was supposed to be 15 from adding, it's almost never 15.

By evenly split out, I mean I want the action to be done all at the same time, I want the actions to be done split evenly out the second.

(I'm doing a different action, not increasing a variable. I just did that for the example)

Using os.time() == oldTime is very unreliable, as the oldTime could be something like 100000.5 and os.time() could be 100001. Meaning, it has only .5 seconds to take those 15 actions.

There's a simple solution to this. You just add + 1 second to oldTime and check if os.time() is lower or equal to oldTime.

As for the 15 actions, you need to check if iteration == 15.

local oldTime = os.time() + 1;
local amount = 15;
local iteration = 0;

while os.time() <= oldTime do
    wait(1 / amount);
    iteration += 1;
	if iteration == 15 then
		break
	end
end;

print(iteration)