These filters compare the price of the last print to the high and the low for the day.  This is expressed as a percentage.  100 means the last print was at the high for the day, 0 means the last print was the low.  50 means that the last print was half way between the high and the low.

Normally the daily high and low only update during normal market hours.  This is determined by the exchanges.  Before the market is open, this filter is not available.  If you want to see any alerts before the market opens, do not fill in a value for either of these filters.

These filters are available after market hours, even though the high and the low do not update.  It is possible for the value to be above 100% or below 0% if the price continues to go up or down after the close.  It is also possible to see these values during market hours, although that is far less common.  The best way to see stocks trading on highs is to set the minimum filter to 100 and leave the maximum filter blank.