On a service, Time segments is how you split a long appointment — for example
a colour: a short hands-on application, processing time where the chair is
occupied but you are free, then a hands-on rinse. You now see those steps as
a colour-coded bar, with everyday labels instead of technical flags.

When steps are saved, their total is the booking length. If that total does
not match the duration listed on the service, you get a clear warning so the
calendar and the listed duration cannot silently disagree.