Hello ​@Cedric LJ ,

Its quite tough to optimize the formula without all the context but I’ll give it a try!
The issue is the ADD L9, this puts your value on each item of that dimension. 
If you use the IFDEFINED as in the example below, it should work more quickly. 
If this doesn’t work, please put in a support ticket, as our support team can look directly into your model (if you grant them access)


 

ROUNDUP(
  IFBLANK(
    (
      (
IFDEFINED('L9 - P&L' = 'L9 - P&L'."Wallet fees",
        ( 'Wallet Lifetime Value' * 0.7 )
        - 'Input Wallet Upfront'
      )
      /
IFDEFINED('L9 - P&L' = 'L9 - P&L'."Wallet fees",
      'Wallet Lifetime'
      [BY: 'SalesForce opportunities'.'Activity level 2']
)    
)
    [FILTER: CURRENTVALUE >= 0],
    blank
  ),
  2
)