In internet parlance, couple is just a generalisation of 2 or more days.At 4 mbps, he could practically download around 1.5GB per hour. That's like 36 GB per day but when you download, there will be a bit more data sent and received than the actual download. Airtel will in any case show data usage than you actually download. You can safely say that at full throttle, around 40GB will be spent per day. He can consume 97 in under 3 days.