Adding the next number and then enter would provide the result.
What most people still don't know is that QuickBooks Online (QBO) also has this functionality. While a little calculation window doesn't pop up, you can still use any of the character functions in a quantity or amount field, add a number, and then the TAB key (the Enter key doesn't work here).
You can even do multiple calculations by inputting another character function, a number, character, number, on so on. It is not until you key the TAB button that it completes the calculation and provides a total.