Imagine performing a voltage measurement at a computer USB port using a Fluke 8846A or 8588A Digital Multimeter that shows 4.8765V. Do you question this reading as you are expecting a good 5V ± 5% (± 0.25V)? And Sometimes, when you try to do the same measurement again (either at other room, or by another person, or using different set of test leads, or applying another probing method, etc.), and you may get another set of reading that may be “closer to or further away” from the expected value?
If yes, you are not alone – as this situation often happens prominently when you are doing high-precision calibration and measurement work.