It's something +/- like this:
autobonus "{ bonus bIgnoreDefRace,RC_NonBoss; }",50,5000;effect when equipped{what the effect does}, chance/10,time activated in seconds/1000;
autobonus "{ bonus bIgnoreDefRace - Using this gear gives you the bonus of ignore the defence of a race
RC_NonBoss - Race Chosen is everything that is non-boss/non-miniboss
50 - 5% to happen[50/10=5]
5000 - 5 seconds[5000/1000 = 5]
So you end with:
Ignore non-boss monster defence for 5 seconds at a 5% chance