"Provisional shift" is the name we give to shifts where an employer knows they'll need staff but may need to confirm some details of the role closer to the day.
Usually, they'll need to confirm the exact length of the shift or the number of staff they need on the day. This means a shift might be longer or shorter than what's listed in the job description or, in really rare circumstances, cancelled in advance.
Because we can't guarantee all the details of these shifts, to keep things fair, you're free to cancel a provisional shift if you need to - without the risk of receiving a strike. This only applies to provisional shifts, which will be clearly labelled in the job description. The normal 3 in 10 rules must be followed for all other shifts.