When Michelle & Jo write their first guess of the count of dried limes of 1,513 on the blackboard, they write it with the bottom of the 3 lower than the other numbers, but in the next shot, a close-up of the blackboard, it is the first 1 and not the 3 whose bottom is below the other numbers.
When Sarah writes her guess of the count of dried limes of 1,489 on the blackboard, she does it on the right-hand side, but the next shot, a close-up of the blackboard, shows the number being written on the left-hand side.