miles to empty digital dispaly

[angiepm2016]

i have a 2014 fiesta, bought it brand new. this has happened twice to me now in the past year, first time it fixed itself same day, im on day 3 now of the issue still current. i had about 40miles to empty in my tank this past monday, i put gas in it to get me thru the week. not until halfway home did the gas gauge move to the amount of gas i put in, then the miles to empty, which i always have on display, kept going under the 40 original miles. i travel to and from work 14miles approx each way, its now at 32, so its way off for 3 days of driving. any suggestions as to what this could be,easy fix, costly fix, HELP! if you see below, i clearly have way more than 31 miles to empty, that is actually about 120 or so miles to empty in my tank. please someone help me fix this