What does this mean?

I know what an excavator is, but I have no idea about their sizing. (And a quick Google search didn't yield a conclusive answer.)

But that may not be a problem for the person offering the "Excavator Service". They are probably selling their services as a subcontractor to larger firms in the construction trade. That is one of the issues of B2B marketing. Quite often the people in a specialized industry use jargon that might as well be  foreign language to outsiders.

And that is what I am, an outsider, so there is no need for me to know what what "Size 60 Machine" means. But still, I am a bit curious.