Can you please explain the "ROLL 6d6 TO DETERMINE ITS CONTENTS" part as this makes no sense to me.
You clearly aren't rolling 6d6 and adding them together because the table goes from 11-66 and that would be a table between 6 and 36.
This would make sense if it said something to the effect of "roll 3 times, 2d6 and treat whichever dice is to the left as a ten's die" but it doesn't say that and as a result to anyone who doesn't recognize how this is supposed to work it is liable to end up confusing.
The Safe Box table is neat but I think it needs a rules revision to better explain itself.