Generally for application over coloured slips or underglazes. If underglazes are applied to bisque ware they should be bisque fired again for even application of glaze.
Our dipping glaze is charged by item weight, in multiples of 50grams. Our minimum weight per item is 250grams (dry weight), so you need to start with 'five units' and then add a unit for every 50grams. So an item weighing 520grams would be 11x 50gram units.