Minecraft wiki entry for Pulse, associated text: Each stackable item, 16-stackable item and unstackable item in the middle hopper adds 8 ticks (0.8 seconds), 32 ticks or 256 ticks to the output pulse respectively. The output pulse can be fine-tuned by increasing the delay on the 1-tick repeater by up to 3 ticks, decreasing the delay on the 4-tick repeater by up to 3 ticks, or by replacing the 4-tick repeater with a block to decrease the delay by 4 ticks (these adjustments affect the total pulse duration, not per item, allowing pulse durations of any tick amount from 5 ticks to 256 seconds).