This is the payroll for the people who run the fief, which includes clerks, reeves, bailiffs, servants at your manor/chateau, town officials (plus what the towns and cities collect via the "town tax" for their own officials), game wardens and the like. Also included are "gifts" given to local worthies to maintain their loyalty. The officials are the folks that collect the taxes and see that things get done.

If you spend less than 4 ducats per capita per season on officials, it will have an adverse effect on loyalty and taxes collected. Too little spent on officials will also increase graft, which comes out of YOUR tax revenues. Officials would average about 6,000 ducats a year (or 1,500 per season). This gives you several hundred officials on the payroll for this fief. Some of them, like the bailiff, were VERY well paid. The maximum you can spend per capita is 4 ducats per capita per season.