Laptop battery stops charging at 79% instead of 80%

I keep my laptop plugged in most of the time and have the "stop charging at 80%" option enabled in Lenovo Vantage. But instead of stopping at 80%, it consistently stops at 79%—sometimes even lower.

Is this normal behavior, or is something off with the battery or the charging management? I've had a similar issue before where it wouldn't hit 100%, but I already sorted that out. This one's new.

Anyone else dealing with this or know if it's something to worry about?