Hey there,
Turbo short power max (PL1) and turbo long power max (PL2) refer to the power requirements of your CPU. PL1 is the power needed to run your CPU at 'stock' speeds. PL2 is the higher rating which equates to your CPU max boost clocks. When your CPU dials up, it will go through PL1 to PL2, which will increase the CPU speed, but also the heat output from the CPU. Your 'boost' speed will be for a set duration (TAU), this is typically about 26 seconds. Once this 26s period runs out your CPU will default back to PL1 to reduce temps. This is known as thermal throttling.
Increasing this number with Intel XTU will increase the power limits of your CPU, and will allow the CPU to boost higher. This will come at the expense of heat and higher fan noise.
If you wish to play around with your CPU, voltages, turbo long/short max, then I'd advise you to use Throttlestop. It has more options, and better functionality.