RDP Cookie Question

We use RDP Persistence with our LTM's. As you probably know, the Microsoft RDP client sends a routing token that contains a cookie which is limited to 9 characters by Microsoft. For example, if the value is domain\johnsmith, then the Cookie:mstshash=domain\jo would be sent. Just the other day, I noticed in the persistence records on the LTM, that there was an entry that was longer than the usual 9 characters. Since our users have the domain name first, and lets say our domain is called newcompany, I am use to seeing the persistence value as newcompan. But in this case one entry showed up as newcompany\johnsmith.agency1. How is that possible?

Thanks