This shows a more or less precise reading of the signal strength denoted in dBm or asu. However in future Android builds, it seems that Google is giving carriers the option to hide the signal strength from users. This is according to a report from XDA in which it has been suggested that future builds of Android starting with Android P could see carriers hide that option from users.
XDA notes that this is slightly different from the tweaks that carriers sometimes make to branded phones and could be applied to all phones on their network just by inserting the carrier’s SIM into the handset. As to why they are doing this is unclear, maybe they don’t want users to get confused between the numbers they see versus the signal bars on their phone, but the option is there should carriers want to take advantage of it.
The good news is that XDA mentions that this won’t affect the APIs that some apps use to display signal strength, so should carriers decide to implement this, users can always turn to third-party apps for that information. Whether or not carriers will go ahead and do this remains to be seen, but like we said, it appears to be something that will only be applied to the next Android build which will most likely be released in the later part of 2018.