The Process Summary dialog provides an overview of all the chosen settings for an image variant or variants before processing. This includes the processed image size, file name, file format, and predicted file size. Any red highlighted figures are there as a warning that something will not be processed as expected. Check the highlighted figures and make the necessary alterations (e.g. change the dimensions), before processing the variants.
NOTE: With the release of Capture One 21 (14.3.0) Output tool tab has been removed and all export tools have been moved into the Exporter. The Exporter gathers all options for exporting photos from Capture One. Process Summary tool has been renamed as a Summary tool.