Until I've taken mine apart to replace the strings I am only guessing at the routing.
However what I think is...
Top and second down strings are anchored in the rear vertical, thread through the fly screen, thread down the movable vertical and out of that forwards along the lower runner, round the end of the runner downwards through the centre open ended slot, back into the runner through the outer open ended slot and onto the anchor screws.
Bottom and second up strings are anchored in the rear vertical, thread through the fly screen, thread up the movable vertical and out forwards along the upper runner and anchor in the front plastic assembly of the upper runner.
Bear in mind that is only how I think mine is assembled and now both upper strings are broken at the bottom caused by grit in the lower runner. I intend to try to replace them with either 0.8mm or 1.1mm Kevlar kite string. If you hear of an atomic explosion over Telford some time in the next couple of months you will know that I am not having any luck with the job!
