Need a septic tank interpreter

After pumping our septic tank the aged company owner remarked to my husband, "pretty dirty." Husband did not ask for clarification and we're too embarrassed to call the man 2 weeks and probably dozens of septic tanks later to ask, "were you just making small talk or does "dirty" have a particular connotation relative to a septic tank?"

So I'll ask you folks instead. Do septic tanks vary in "dirtiness" and, if so, what constitutes a high level of dirtiness? The amount of solids?

I would have simply interpreted what he said as "Pretty dirty, sure did need to be pumped out. Good thing you called us before things got worse."