Interesting. I wonder if that appears between the minimum and maximum fare. Trouble is, if it doesn't show what the balance is then how do you know whether you've got enough? Was it only on entry, or exit, or both?
[1] These are the older design of electric gates, typically found at LU stations outside of Zone 1 and were installed in the late 90s/early 2000s.
If the E1's are the same ones used at Surrey Quays (except for the wide gate), they can also show the total and a near expiry message of a season ticket too.
On a similar but off topic note, we tapped in to a wrong entrance at one of the Underground stations then had to tap back out charging the maximum possible fare, but when we got off at the intended station it did a sort of refund when tapping out at those gates which was slightly confusing!![]()