Probem with dax calculation to reduce values from total

[senorbol]

Hi All, 

I wondered if someone could help with an issue I have with a dax calculation. My DAX skills are fairly basic so hoping an expert can solve this issue. 

I've got data where I need to make up a total of a certain type of asset and display this per quarter - there is then another value which shows reduction in this asset per quarter - I've got as far as detailed below but the issue I'm having is when the reductions start if there are no further reductions in future dates then the value goes back to the total. 

Details and explanation here:

As you can see from the screenshot - the burndown forecast is correct up until Q1 2022 - but as there are no further reductions my forecast value returns to 50. What I want to achieve is the burndown forecast value to remain at the reduced value - 2022 Q2, Q3 and Q4 would show as 5 until the further reduction of 1 in 2022 Q4 which should then give me a value of 4.

Here are the dax calcs I've used.

Cumulative Output =

CALCULATE([ST_Count] ,

FILTER( ALLSELECTED ('Calendar'), 'Calendar'[Date] <= MAX ('Calendar'[Date])-1)

) +0

Output 2BC = 

CALCULATE([ST_Count] , ALLEXCEPT('Master Data 2', 'Master Data 2'[Service Type Bucket 2], 'Master Data 2'[CSP_OOS_Fix] ))

Burndown Forecast = [Output2BC] - [Cumulative output]

Any help on this would be greatly appreciated. Also if you require any further info please let me know. 

Thanks

[lbendlin]

Your Quarter column needs to be a YearQuarter column.  2021Q1  etc.