That's the time since the first campaigns in the area under development if I understand it correctly, which is a very different thing. Large developments in archaeologically dense areas will often have multiple sites associated with them. I've seen e.g. hundreds associated with airport expansions.

Back when I did rescue archeology, 2 days was a lot closer to the time spent on a specific site than 8 years. 1w-2mo is more typical, but the parts I can read don't make clear whether 2 days was the entire extent of the excavations, it's just a narrative entry point where they're rushing to finish before they leave.