RN314 and Multiple MacBook TimeMachine backups

[PWS442]

I have 2 MacBook Pros that use Time Machine for backups. I use two Airport Time Capsules, and one ReadyNAS. I have just retired one of the Macs, and successfully deleted their sparsebundles from the Time Capsules. However, I only see one on the ReadyNAS, and it seems to be a combined file, indicated by the size.

Did I do something wrong? Not that I need the ReadyNAS space, I have 20TB free!

However, short of starting over (which I seem to have to do now and then), how can I solve this?

(BTW: this article does not seem to work exactly as shown: https://kb.netgear.com/7053/ReadyNAS-Removing-Time-Machine-data)

Thanks for any help.