When I trained as an accountant, precision with data was drummed into us. Not just because accounts need to be accurate. But if we used the common 5 up 4 down rounding in reports it inevitably led to this type of complaint.
So in this case, I suggest that it is best to always round down. Assuming that this is fairly easy to change in Flarum.
62.63 years old. But I don’t object to 62 or 63.