Power in erg mode too high

I have stages sb20 and use as power meters garmin pedals. When I launch Zwift I select controllable sb20 then in power meter and cadence select garmin pedals. All connects fine. When I go into erg mode the power needed is higher than the target. Like 220w when the target is 200w. It basically means I get too tired notably on hiit workouts, can’t finish. Can anybody help here? Thanks :pray:t2: