holiday entitlement changes

[world class male]

we recently got our new holiday sheets which is now worked out in hours not days off.
few things that stick out is once you've booked your basic 4 weeks off out of 23 1/2 days entitlement , you're now left with an odd amount depending on what your "day off" will be when on leave,
how can they plan this forward with reserves when they don't know it themselves until fri/sat?
also what happens to all the maths when we drop down to 38 hours?
you may also have what you think is 1 day left owing to take but refused a weds off because you've 8hrs left but that day uses up 8hrs 30?
we've also had our daily start times changed twice recently, what happens when it alters again and you could end up owing them if a future booked day off hours get reduced at a later date!
this system seems stupid working with rotation days off never mind random days off.
they seemed to get it up and running pretty quick, against the cwu wishes according to our rep, when are they going to stop reserves getting too many regular tuesdays off and working 40 hours for 39 hours pay or give them a later start time on saturday or pay overtime to start when others do?