The modelling projection from the chief economist does not include a projection on jobs. I think the model assumes full employment, and that's how it generates its figures.
The practice that it has occasionally used is that you take the GDP figure and then take that as a percentage of total employment in the economy. I think that works out to roughly 10,000. You may have seen the figure of 10,000. That's where it would come from. That's the equivalent of what a GDP increase of $1.7 billion would generate.