Hi Tpete,
I'm not really clear from your post what the issue is - which may explain why you've not received a reply.
A stop sell order is an order placed below the current price which, if triggered, becomes a market order to sell the instrument in the expectation that price continues to fall lower so that you can buy back at a profit. The point to note is that it is not guaranteed to trigger at the price you set. If the market is moving fast, you can experience 'slippage', which means the order is filled at a lower price than the one you set. This tends not to be a major concern for swing and position traders looking to trade large moves over days or weeks, but it is a major problem for day traders looking to capture much smaller moves and for whom precision entries and exits make a huge difference.
The day's range is the number of points between the lowest low of the day and the highest high of the day, so you are correct in saying this is "the max and min the stocks are traded at". Needless to say, this varies from day to day. My guess is that you've been filled at a price which appears on your charting software to be below the low of the day's range which, theoretically, isn't possible. Is this the point? If so, the spread - especially if you're using a broker with variable spreads - is likely to be the answer. The reason being that spreads get wider when the market is volatile and contract when it's range bound and going nowhere. The chart doesn't take account of this, i.e. the spread can be above or below where price prints on the chart.
To conclude, I think you were just unlucky and your stop sell order got triggered at pretty much the exact low of the day. If it's any consolation, when I day traded U.S. equities yonks ago, I managed to buy the exact high of a stock - to the tick - AND sell short the exact low of the SAME stock (over $2.00 apart) - to the tick - on the SAME day. In all my years on T2W, no one has ever managed to equal this incredible achievement - let alone better it! ;-)
Tim.