Honda Mower Variations

Can any one tell me what the difference is between models HRR216 K9VKAA, K10VKAA, and a K11VKAA Honda mowers. I looked a model HRR216K11VKAA and by the time I bought the mower I got home with a HRR216K10VKAA. I'm sure the differences are minor, but I'm curious. Thank you.

As I understand it, the K number is basically a revision, with the K11 being a newer variant than the K10. Typically no huge changes, but hard to say without checking the service manuals.