The Price vs. 52 Week High indicator compares the current price to the highest price at which the stock has traded at in the last 52 weeks (12 months), ie. the formula is : Current Price - 52 week High / 52 Week High.
To screen for companies that are within 10% of their 52wk high, the criteria would be Price vs. 52 Week High > -10 (i.e. greater / less negative than -10%). Here's a sample screen that you can fork.
Alternatively, if you wanted to set an alert for when a stock has fallen more than 20% below its high, you would set it for Price vs. 52 Week High < -20. Although the targeted value is numerically greater than 20, because it's a negative number, it needs to be shown as "less than".
Academic research has shown that stocks close to their 52 week highs tend to outperform. This is apparently because investors use the 52- week high as an "anchor" against which they value stocks, thus they tend to be reluctant to buy a stock as it nears this point regardless of new positive information. As a result, investors underreact when stock prices approach the 52-week high, and consequently, contrary to most investors' expectations, stocks near their 52-week highs tend to be systematically undervalued.