The makers of resistors are conning us all! It goes like this:

If you have a resistor with a stated tolerance of 10%, and a stated resistance of 100 Ohms, you might imagine that
you've bought a part that will have an actual resistance somewhere between 90 and 110 Ohms.

However, the firm also makes resistors with a tolerance of 5%. These will be taken from the same batch as your 10%
effort. So you can say with certainty that your resistor is either between 90 and 95 Ohms or 105 and 110 Ohms.

So if you have a part that isn't the highest spec available, you *know* that the one value it won't have is
the
stated one.