Unfortunately, the Join tool in Alteryx doesn't allow the option to join on non-equivalent conditions (like greater than & less than). This post has a good solution that should work for you using the Generate Rows tool: https://community.alteryx.com/t5/Alteryx-Designer-Discussions/Count-working-days/td-p/672159
Another way to work around this is to generate all possible joined result rows using the Append Fields tool, then Filter back down to the rows that actually meet the desired criteria. Then just Summarize to count the joined rows. I've attached a sample workflow using this method.