Shall I explain the £4,300 claim its easy.
They looked at a situation in which the UK would have the same deal as Canada.
They then looked at GDP predictions for both remaining in the EU, and on the deal from Canada.
They then used GDP per capita to divide both predictions up.
They then multiplied it by the size of the average household in the UK currently and came up with the figure and looked at the difference.
Its a projection, based on available data. Still not an outright lie like the £350 million, or £600 million a week figures .