I had not, sorry about that and thanks for the reminder.
I think the error message is misleading us. The only thing I see wrong is that you cannot concatenate a string with a plural -
"some string" & pathnames does not work.
concatenation "%0d%0a" of ("rd /s /q %22" & pathname of it & "%22") of find folders "*" whose ((last 2 of pathname of it as integer) <28) of folder "c:\temp"