In the bar, Ellie tells Grayson to "Turn around, walk 10 paces then stop." Grayson turns and only takes 3-4 steps.
There is some ambiguity regarding the definition of a pace - it can refer either to a single step (1 foot) or both feet, where the pace starts when the first foot leaves the ground and ends when the same foot touches again.
In either case, Grayson did not go far enough.