Next to the door to the bus there is a screen which can show the numbers being called for the next bus. When I was there the numbers stayed as "0 to 0" as it wasn't busy at that time, I can't say whether the numbers are being used at peak times or not.
I can answer that. We arrived, got tickets and there was a bus already there. We did not have numbers for that bus but had no problem getting on- despite the ticket being checked.