It's normal brother, Time do not go the same all the time, Some times your gig will rank high and sometimes low,
It's to make sure other sellers get a chance as well.
Once my impression was around 500 a Day then times went bad and instead of 500+ a day, I was getting around 600-800 impressions a week, After a while, again my gig started ranking and went from 70 a day to around 4000 a day, Again since last week my impressions went down again Now its around 1800 a day. So it's a normal thing.
Please do not change your ranked gig too much, It may round your GIG. Keep patience, my friend.
Thank You.