Call activity is considered bullish when the majority of the trades are executed near or at the ask price. This is considered buyer driven behavior as the buyers are paying whatever the sellers are asking.
The same is true for puts. Activity is considered bearish when the trades are executed near or at the as price.
You should be especially careful with this screener. Double check my note about the bid-ask spread above and then also be aware that these screeners do not exclude options that were placed as part of a spread trade. All option orders print as single legs, so there is some trickery to do to determine with high probability whether or not an option was part of a spread, but it is all guesswork.