Once you have coded and entered the Other Deduction, you can then go to the Special Allocations tab, which will show a line item for Others.

Click on Others, you will see the Total Available amount on the right.  You can choose to either override the allocation by Amount or Percentage.

See this article for detailed instructions of how this works: https://proconnect.intuit.com/community/partnership/help/how-do-i-use-special-allocations-in-proconn...