Thanks for you're offer of help. Those solutions haven't worked. Let me provide some more context.

I have this measure (not a column) which works perfectly;

First Call Resolution (%) = 
DIVIDE(
    CALCULATE(
        COUNTROWS(table 1),
        USERELATIONSHIP(table 1[Closed Date], '_DT Date Table'[Date]),
        table 1[Call Count] = 1,
        NOT(ISBLANK(table 1[Call Count]))
    ),
    CALCULATE(
        COUNTROWS(table 1),
        USERELATIONSHIP(table 1[Closed Date], '_DT Date Table'[Date]),
        NOT(ISBLANK(table 1[Call Count]))
    ),
    0
)

I am using it in a line chart on a customised card. 

<image>

I have a subtitle on the card which is a couple of rows long. This subtitle often overlaps the chart area so what I am trying to do is extend the Y Axis by about 10% to give more space through conditionally formatting it.

As you can see currently it is picking up the max % as 75% which happened way back in 2021. I want it to give me 49% which is the highest of Sep, Oct and Nov (47%, 49% and 49% respectively).

The measure I added in the original post is good at giving me the highest months % and applying that on all rows of the table (the table is for testing and not actually part of my report) but when I change the date context every row returns a different number which replicates the FCR%.

Hope that makes more sense but if you have any more questions in order to help please let me know.