Everything i can find says that <0.90 is negative for the Herpeselect test. How can I know for sure that <0.91 is still negative? Does this higher number mean it is closer to equivocal or positive?
The number does not mean "amount of antibodies in blood" or anything like that, so you should really forget about the whole question. Negative is negative as long as a test is confirmed to be positive, and in this case a positive result would have a value of 1.1 or more.
You do not mention of having a test result of exact 0.91, but if you have had one, I see no reason to be re-tested if the test was done after a proper time after possible exposure (3 months). It's a negative result.