Description 
The Fibonacci retracement lines are ranges computed from the high and low over a given period of time. The actual lines that are drawn are specific percent retracements from the given high or low. Investors primarily look at 3 different lines (0.382,0.50,0.618), which are based on the historical formula for the Fibonacci sequence.
These Fibonacci retracements can occur both after a recent downturn or swing low; or after a runup. The actual target values are computed by taking a percent change from the high or low value.
By specifying Fibonacci Down on StockFetcher, you are referring to the retracement lines drawn after a recent swing low. All of the values will be relative to how much the stock has recovered from the recent low. For the Fibonacci Up, the values are based upon a recent runup in the stock price. Again, the actual values refer to the amount the stock has moved to return to the recent low.
Below is an example of the Fibonacci Down screen:
The actual values returned by StockFetcher are computed from the most recent close in reference to the recent high or low. In the example above, the value returned by the screen wold be near 0.382 (the most recent close is very near the 0.382 Fibonacci band.)
Note: When spcecifying the Fibonacci Up, the values returned will be reversed from the Fibonacci Down. So a filter scanning for crossed above in the Fibonacci Up case will actually result in a downward price move.
StockFetcher allows several parameters with the Fibonacci retracements.
time  The first parameter is the length of time used to look for the uptrend or downtrend. So, a value of 65 will search over the last 3 months to look for the trend.
min length  The second parameter is the minimum number of days for the trend to occur. For example, if you specify 15 days here, that means the distance between the high and low must be at least 15 days.
labels on/off  Finally, by setting the third or last parameter to 0, you can eliminate the labels that are seen on the charts; this may help to clear up your chart if needed.
