Minecraft wiki entry for Memory, associated text: L4 and L7 are basically two opposite halves of the same machine — both are extremely compact and customizable tick-wise but L4 is made for off-pulses with durations ranging from 2 to 8 redstone ticks while L7 is made for on-pulses with durations that are 9+ redstone ticks long which includes the 10-tick stone button. Customizing each requires changing the repeater delay or adding repeaters to match the trigger duration.