Drawing the outlet for my model.

[Shakshyam Kafle]

I am trying to create a watershed and I have these two monitored outlets(black circle on the oicture) for tile drains for phosphorous monitoring . Are these the same outlet I chose for my watershed outlet because no stream passes through these outlets. 
I am generally curious about where to put my outlet point? 
Initially I put my outlet where my monitored tile drain outlets are located, but it generated watershed too far below outside the field under the study. 
Then I put my outlet at the pin circle which somehow incorporates the field under study.
Can you help me how do I create subareas by chosing the right outlet.