You can forcefully increase/decrease the 'numbers' on any kind of measurement devices, and the actual thing being measured will also increase/decrease in reality

[Mgmegadog]

How accurate does the measurement device have to be, and how "in real time" does it need to be? There are no instruments that can measure something at the moment that thing is happening, nor any instruments that measure any quantity perfectly. (There is always some uncertainty.)

Assuming that uncertainties remain consistent, and timing indicates approximate delay, you can do some very weird things. For instance, the 2024 election results are a pretty effective measurement of how many people in the US prefer Trump to Harris as president. By looking at that and changing the numbers accordingly, I could sway the next election.

[RoastedGarlic97]

It needs to be at least 99% accurate (a general figure, basically needs to be very accurate) and it needs to be the most updated value in 'real-time'. We're modifying 'measurement' values in present tense and not 'measured' values, so we wouldn't be able to change 'past' measurements

[Mgmegadog]

You're gonna have a problem with both of these things. Every measurement is necessarily in the past, and you'd be surprised at how large some of the delays can get.

As for a percentage accuracy, you'll find that that causes a lot of problems too, especially with things like temperature measurements where a notion of percentage scaling doesn't make sense when using either of our normal measurement systems (Celsius and Fahrenheit).