If your grow medium is oversaturated and water still remains in your bottom tray 30-mins after watering, carefully remove the top and bottom grow trays and tip the remaining water out over a sink, making sure not to let any of the soil/seed spill out. Hold off on watering for the next day or so until your greens absorb the remaining water left in your coir. In general, it's better to underwater than to overwater as microgreens will recover more easily from underwatering.