Need to see actual data for detail analysis, but if "offers" are calculated field which is back calculated from Hires,
340 / 77.10% = 440.9 is understandable.
I've ran into the same issue in the past.
I was able to fix mine by adjusting the granularity of my blending. This will only help if you're blending data sources.
You can also try using WINDOW_SUM by editing the pill on the shelf.
It may be easier to understand and help if you could include a packaged workbook as an example.
It is the other way - 77.10% = 340/441.
Offers is a calculated variable by counting unique ID in a table. The challenge here is that all the numbers in each row is correct. Total should be displayed to 451 not 441.
Are you able to add sample data as packaged workbook?