This ReferenceNumber represents a comment. When you go to your landlord, just tell him you want a referencenumber, sign an agreement, and then when you call him through online banking, just fill in the referencenumber.

In fact, the purpose is to facilitate the landlord to see who paid him, otherwise the landlord may charge a lot of money a day and can't tell who is who. So this referencenumber can prove your identity. Everyone has a referencenumber, which is recorded in the landlord's hand, and the landlord gave you the number. When you go to the bank, the bank staff doesn't know your landlord, of course not.