According to the UK online "Bookmaking" Dictionary:
filled in /ˌfɪl ˈɪn/ phrasal verb of fill
1. to lay a winning selection to absolute buttons but capitalise on the tiny loss via free television marketing e.g. "we got filled in when we accepted £1.33 at 16/1 but we used the situation to pretend we take real bets" 2. to lose a fraction of your daily profit from addictive games of chance on a horse race. e.g. "we take £1000's all day long on the roulette and the slots but we got filled in for £20 on a horse race"
According to the UK online "Bookmaking" Dictionary:filled in/ˌfɪl ˈɪn/phrasal verb of fill1.to lay a winning selection to absolute buttons but capitalise on the tiny loss via free television marketinge.g. "we got filled in when we accepted £1.33