@JackB116 I'd actually suggest changing your card from a Pivot Table to a Table chart type if you want to add calculations. You'd need to use beast modes for your 2022 and 2023 totals like this:

sum(case when `Delivery Year` = '2022' then `GDP Net` else 0 end)

Then your % difference calculation would look like this:

(
sum(case when `Delivery Year` = '2023' then `GDP Net` else 0 end) 
- 
sum(case when `Delivery Year` = '2022' then `GDP Net` else 0 end)
) / 
sum(case when `Delivery Year` = '2022' then `GDP Net` else 0 end)