It should adjust down to about 60lbs on 4 rotations of the limb bolts. DO NOT rotate the limb bolts more than 4 turns from dead tight. EVER!!! The bow becomes very dangerous, as the limb bolts may come loose when you draw it back, or even before. There is a lot of energy stored in a strung bow. You could be seriously injured if a limb bolt comes loose and the bow is not in a bow vise.
Also, when you are adjusting the draw weight on a bow, only turn each limb bolt one revolution or less and then go to the next one, alternating between the two. Pay careful attention to each turn making sure to only go exactly the same amount on each limb bolt. If you happen to go a little more or a little less on one and not the other, your cams could get out of time thus making you bow very inconsistent when shooting.
If this happens, you may feel a double "clunk" when you draw the bow instead of a smooth single "clunk" when the cams break over to their natural full draw position. To correct this, tighten both limb bolts back down to dead tight and start over. Never shoot the bow with limb bolts dead tight either, always back them off at least 1/4 turn each.
It's always best to take your bow in to a professional when any kind of adjustments are made, unless you really know what you're doing.
I hope this helps.