Graphical Actual Execution Plan - Estimated vs Actual number of rows
The number 17 comes from the estimated number of rows (per execution) multiplied by the estimated number of executions.

3.85562 * 4.37149  =  16.8548043  ~=  17


In SentryOne Plan Explorer,* we perform the conversion for you, so that estimated rows simply starts at 17, not 3.85562 (I didn't try this specific plan, but that's how the logic in the code should work). I describe the reasoning behind this in this blog post, back when the fix first appeared in Plan Explorer.


  *Disclaimer: I work for SentryOne.