Very simple. Bo Wirebrand (Vetlanda team manager) picks seven riders that fits under the average cap (10.500, based on season entry average).
Of those Emil and Jacob Thorssell are the two with the lowest floating average which means that those two will be the reserves for this meeting.
Next week the averages might have have changed so that Emil is back into 1.5's with another rider at reserve.
Btw enjoy while you can this is probably the last season in many years with such strong lineups.