What you see in the UI doesn’t necessarily match what’s actually happening in the device. It’s all just programmatic interpretation.
When you see 100% charged, that could just be 90% of the battery, but it’s 100% of what the device will let you charge it to.
Similarly, what a phone shows as 1/2/3/4/5 bars of signal doesn’t necessarily match what you might think it does. They just pick a signal level and set that as a threshold for a bar, and if you meet it, that’s what it shows you, but the range between the levels can be pretty diverse, and sometimes is even patched between versions. I know some phones have had complaints about always having poor signal, and the ‘fix’ was basically a software update lowering the threshold so that it showed more bars more often.
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