This is what has been put on Espncricinfo Commentary section:
"A fair few messages asking how and why the target is less than England scored? It is because England's innings was wrecked before the rain came, and therefore the loss of overs was actually to their advantage, as they were able to play more aggressively on the resumption, knowing that they didn't have to survive for 25 overs. Had they continued in a 50-over game from 79 for 7, they might well have been bowled out more cheaply."