Laser head focal length

Hello everyone – I got my first Laser,(ortur M2 - 7 watt) about 10 days ago. I really am having a good time
time with it So much fun that my 15 watt came in yesterday. I finally got it focused in today. My 7 watt focus range is around 7-7.5 mm. All the different videos that I watched said about 7-7.5 mm. It turns out that my 15 watt is only 4-4.5 mm. (measured from the bottom of the heat sink cooling fins down to my subject). Is that normal when you start stepping up in power?