I know you're keen for an update, so...
I spoke to the bloke on Monday. He said that by "average" he did indeed mean "total". Easy mistake to make.
And by "Man Days" he meant "Development Days" which does include all 3 roles. So it is 15 days.
Which is clear bullshit, he's made a mistake and is doubling down on it and lying to cover his ineptitude. But whatever!