Formatting FLR as a percentage in Power BI

Question

I'm working with SQL data out of ServiceNow. I'm trying to create a visual for FLR percentage by supervisor by date. My FLR code reads:

[FLR %] = LEFT(AVG(CASE WHEN opened_by = resolved_by THEN 1.0
                  ELSE 0 END) * 100, 4) + '%',

Our version of FLR or first line resolution states that when an agent opens and closes and incident it's counted as first line resolution providing the re open count and reassignment count are equal to 0.

Every time I try to add this data to a visual it tries to turn it into a count. I'm trying to find a way to show it as a line graph where the FLR percentage is shown over time and each of the five supervisors is represented by their own 'dot'.