Brother bought a 3150 champ and the amount lagged and took 6000 ip from him

So my brother who started playing more league recently decided to buy Sona at 3150 because he liked playing her during the free rotation this week. He had a little bit over 7000 IP when he bought her but after the purchase, his IP count was at 800. We checked his purchases tab and there she was at 3150 IP with some other 450 IP guys he had bought a few weeks ago but no sign of an unusual transaction.

My brother have been playing a lot to get those IP and I was wondering if there was a known fix for him?