Modulo with integers will always be exact. Hence 4160%64 = 0. Modulo with decimals will be as accurate as the computer can represent it. (tivia: 6.4 cannot be exactly represented with floating point numbers)
416/6.4 is not acctually 6.4 it's 5.399999999999977, but Construct does some rounding so numbers look prettier. For example if you set some text to 416/6.4 you'll get 6.4 and if you set the text to str(416/6.4) you'll get 5.399999999999977.
Back to the issue, it's bad practice to check to see if a floating point value is equal to an exact value.
So instead of this:
The usual method is to do something like this:
Where epsilon is a small number such as 0.00000001. The idea is you don't check if it's exact but rather it's close enough.
When using modulo for example a%b the result will be in the range of 0 to b so to check if the result is close enough to 0 or b you can do an expression like:
abs(a%b - b/2)>b/2-epsilon
Of course I don't think such a formula is needed, but I'm too lazy at the moment to watch the tutorial video to see exactly what they do.
You could re-write your formula for time. I assume speed is in pixels/tick and you're events are something like this:
<img src="https://dl.dropboxusercontent.com/u/5426011/examples19/a.gif" border="0" />
You could rewrite it to be time based so it would run the same speed no mater how many ticks per count, and you'd avoid the cpu math precision issue.
<img src="https://dl.dropboxusercontent.com/u/5426011/examples19/b.gif" border="0" />
The issue now is the platforms aren't always butted up against each other, sometimes there's a gap. So instead you could check the last platform's distance from the edge of the screen to see when to create another platform.
<img src="https://dl.dropboxusercontent.com/u/5426011/examples19/c.gif" border="0" />
No gaps, but with constant 60fps you may run into the need to create more than one platform if the speed exceeds 32*60 or 1920pixels/second. Not sure if the player will die long before that speed. If the issue comes up you could just duplicate the last event for a quick fix.