Is there a document that references the output of the following command..
show ppp queues??
in IOS there are internal data structures that may or may not be documented for the end user.
You can find hundreds of commands and output that are either undocumented, obscure or confusing. In most cases the commands are hidden, but they can also be made visible occasionally.
It is normal (in my opinion) that cisco doesn't have an obligation to disclose all these internals meant for the TAC and engineering.
It seems to me that no errors are reported in the output above, so you should be fine.