Surely this figure should be the allowance for a couple which would be about £95 per week
I have no inside knowledge of how the approval system works, so this is just my opinion. One has to assume, case workers are trained and have guidelines to work to... particularly regarding financial matters. Although not an interpretation of the law, a case won on appeal would set a precedent.
From the information I've seen on various websites, it would also appear, if the spouse can demonstrate realistic employment prospects in the UK, her potential salary will be taken into account.