Total does not match individual rows For Bay Description

Hi villa1980 - you can adjust each measure to ensure consistent results across individual rows and the total row

Block_Bay_mins =
CALCULATE(
SUM('EXTR_STG_FOCUS APPOINTMENTS'[Blocked_Bay_Mins]),
'EXTR_STG_FOCUS APPOINTMENTS'[Appt_Type] = "Blocked"
)

Booked_Bay_Mins =
CALCULATE(
SUM('EXTR_STG_FOCUS APPOINTMENTS'[Booked_Appt_mins]),
'EXTR_STG_FOCUS APPOINTMENTS'[Appt_Type] = "Booked"
)

CM_Tot_Mins =
SUMX(
VALUES('EXTR_STG_FOCUS APPOINTMENTS'[Centre Name]),
CALCULATE(SUM('Calendar'[CM_Tot_Mins]))
)

you can update cm_available mins to calcualte properly.

CM_Available_Mins =
[CM_Tot_Mins] - ([Block_Bay_mins] + [Booked_Bay_Mins])

Adjust CM_%_Av_Mins to Respect Row and Total Context

CM_%_Av_Mins =
DIVIDE([CM_Available_Mins], [CM_Tot_Mins])

Hope the above calculation helps to solve .