Split shift
A split shift is two blocks of work on the same day, with a gap between them that is longer than a meal break. Lunch service and the evening service, with the afternoon off, is the usual example. The gap is the point. It is not automatically paid, and it is not automatically rest.
Record two shifts, not one long one
If you draw one bar from 11:00 to 22:00, the afternoon looks like work. It was not. Two shifts on the same date, 11:00–15:00 and 18:00–22:00, tell the truth. In Shiftbrook that is two rows. Each can have its own break minutes. Each stays a draft until you publish it. An open shift can be one of the halves if you know the hours and not the person.
The work hours calculator will total one span if you type one start and one end. Do not do that for a split and then subtract the whole afternoon as a break, unless the person was actually on a break under the contract. A three-hour gap they can leave the building for is not a 20-minute statutory rest break. It is a gap between two shifts.
What the gap is not
Daily rest is the 11 hours between working days for an adult, not the pause in the middle of one day. A split does not satisfy daily rest just because the afternoon was empty. The 11 hours is measured from the end of the last block to the start of the next working day. Weekly rest is a separate 24 hours, or 48 hours a fortnight. Check those joins on the week, not inside the gap.
Pay for the gap depends on the contract and on whether the time counts for the minimum wage. Time the person can spend away from work is not the same as time they must stay at the workplace, available. This page cannot see the contract. If they must remain on site, read the on-call entry and the GOV.UK minimum-wage guidance before you treat the afternoon as unpaid. Shiftbrook does not price either half.