Oh. Hang on.
Turns out "half time", in Blackburn, means 4 days out of the week. But "half stipend post", presumably, means half of what other clergy get paid if they're full time.
The logic is inescapable. If half-time is 4 days, and you still get your weekly day of rest, then a Lancashire Week must consist of nine days. The Church of England eh? Not all the clergy believe in the Virgin Birth. But fitting 9 days into a week is a whole new level of miracle.