Questions about I-131Form, Please help! Thanks

Part 3 Processing information
1. Date of Intended departure -- How to fill out this one if i don't have a exact date yet? Can i just leave it blank?

Part 7
1 "one trip" or "more than one trip? -- I actually plan to use it for "one trip" some time in the following year. But is it more convenient to select "more than one trip" in case i may need it? Does that affect on the approval of I-485 or I-131?

Thank you very much for all your help!

Please also help to confirm fees if i submit them before Aug 17th.

I-485 -- $325 +$70
I-765 -- $180
I-131 -- $170

I really appreciate all your time and help!