Your original value is a floating point number, and you convert to integer, then you use the Should be Equal As Numbers to test if your integer number is equal to the float number 0.0.
The idea of the keyword is to skip directly the step you take to convert to integer. Just compare the numbers. The precision factor is for the internal rounding of decimal values, so if you had 66.56789 it would be rounded to 66.568 (this is my interpretation of the function).
About the real problem you have. It is better to test mathematically the value, for example with:

${valid delta}= Evaluate abs(${delta}) <= 100.0
Should Be True ${valid delta}