Custom Total

tarocha , Assuming these 1,2,3,4 are month no

Try new measures like

averageX(values(Table[Month no]), [Headcount])

calculate([admission], filter(allselected(Table), Table[Month no] = max(Table[Month no] )))

or you can is filtered and push this calculation to grand total

refer:https://powerpivotpro.com/2013/03/hasonevalue-vs-isfiltered-vs-hasonefilter/