This discrepancy was intentional. As each scene is relayed to the viewer from the perspective of a different character (Pumpkin at the beginning & Jules at the end) - and the mix-up with the dialogue is down to each character’s differing perspectives/recollections.

There was a throwaway line before this scene noting how this is their first attempt at a gig since their father’s passing. Just one of the many attentive details of this movie.

As demonstrated by their fixing of the fence in the beginning of the movie. The boys aren't the best at completing their jobs. Which is fortunate later when their laziness leaves a pile of poles next to a boulder for a quick getaway.