Old chargers (non-switchmode), the heavy ones, did suck a little power even when just plugged with nothing charging. But those 5%/95% numbers are just picked out of the air. It would be about how long it takes for the battery in the device to discharge enough to engage the charging circuit again.

In any case, just forget about that - it's totally irrelevant for modern switch-mode chargers. It'll use something if you leave them in for years, but that's about it. As said earlier, any warning message popping up on the device will use (much) more power than saved by disconnecting the charger.

(There are still non-switchmode chargers out there though, for other types of devices. E.g. my laptop charger. It's of the big-transformer type and it's lukewarm even when not in use. Not that it would mean anything to unplug it, because the room is heated by thermostat-controlled electricity in any case.)