Time Span on I-131

I am thinking to apply for the advanced parole for my possible one-month-long trip back to China. But I am not sure when I will go back, it might be between May and June, maybe between July to August, maybe between Dec to Jan. Do you think I can put down "May" as Intended Leave Day and "8 month" for the "Length of the trip in the part 3 of the I-131 form?

Or you have better suggestions,

thanks