@JADinAZ  -  after doing several with zero  - I've since changed how I'm completing the SE deferral. 

1)  For Line 18 - I enter 77% of the net profit  -  (I've read where that is an acceptable method to use)

2) Go to Form 1040 worksheet, Part II, Deferral..Smart Worksheet, Line11      there is where you can amount your client wants to defer