It is logged as simulator time and does not go towards Grand Total Flying Hours or Total Aeronautical Experience.
Having said that, up to 100 hours of simulator time (including up to 25 hours synthetic trainer) can be credited towards your ATPL hours requirements. Therefore, although you don't log it as total time, the first 100 hours does count for something. You can get you ATPL with 1400 TAE + 100 hours simulator.
Another brilliant example of how we make the business of determining whether or not an individual is suitably qualified to command RPT operations confusing to the point of idiocy.