To reduce the Hold Zone size (distance in price between a buy and a sell) you'll need to reduce both the Buy and the Sell SAFE values. After that you can reduce the value of the minimum trade size and reduce the minimum # of shares per trade.
All of these will help narrow the gap between the Buy and Sell recommended prices.
Setting SAFE to zero and min shares and dollars to 1 each would give you the smallest range. Those would be impractical settings, but you can check it to understand the limit.
Reducing the size of the Hold Zone should increase the number of "round trips" trades you get on many stocks, but you need to remember that it also reduces the LIFO gain per round trip. The sweet spot occurs when you get the most round trips at the largest LIFO gain.