I know this because I was told this in no uncertain manner by a lady in the cathedral in Mainz last night.
New Year concert, seats in Row 20.
Identify Row 20 in the usual manner i.e. the number that’s physically attached to the bit you sit on.
“This is a CATHOLIC CHURCH”, she tells me.
Appears that the row number applies to the bit you kneel down on.
No wonder they call them Left Footers.
Good concert, though…