It can be solved if you convert the number to a string and back to a number:
print(tonumber(tostring(-200 * 2.55)) + (255 * 2)) -- 0
Don’t know why this is the case but it works.
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How strange, it seems to be incredibly close to zero though. math.floor would fix it, but it’s still strange.
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The reason for this is because “2.55” can`t actually be written in binary with a finite amount of digits so it has to be rounded resulting in a rounding error, it’s like trying to write 1/7 as a decimal number and trying to do calculations with that.
An example for this in decimal would be expecting this to be true:
0.111111111 * 9 = 1
You (should) get the same exact rounding error with every single programing language that exists when using double-precision floating-point numbers as it is a problem that is inherent to the floating point system itself rather than the programing languages that make use of it.
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This is exactly what I’m looking for, I knew I was missing something really basic. And this isn’t even the first time I accidentally computed a value outside of binary bounds, we live and we learn, thank you thank you 
This is just what is known as a precision error, binary which is the 2-base number system is incapable of representing 2.55.
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You mean math.floor or math.ceil
no I mean math.round
try it yourself it works