BBQ, the starting charge weight is the minimum for the particular bullet listed using a certain powder. The starting 10% lower is used for a maximum listed weight. Say a book gives you 45 grains of varget as a maximum load for a 168 grain bullet in a 308 winchester. So your starting load is 10% less of 45 grains. So you start at 40.5 grains and work your way up carefully.