See if this helps:
LOAD * INLINE [
LOAD 'Total' as F1
If(F1 = 'Total', (Sum(TOTAL F2) - 8), Sum(F2))
=Match(F1, 'Total', 'P1', 'P2', 'P3', 'P4')
Then you would be getting dimension as well and you will be getting breakup of expression values with dimension as well..
What exactly you wanna?
I have bar chart with dimension limit >total ticked. Thats giving me Total bar in last. Can It be possible to put that total bar in start of bar chart as first bar?