KiCad clearance vs JLCPCB clearance
I recently ordered PCBs at JLCPCB with a KiCad design and I ran into exactly the same question.
As @Mat has already pointed out, the clearance of the net classes are copper clearances. Unfortunately you cannot specify more sophisticated clearances in KiCad 5.
If your PCB is very basic and you only uses large parts, I'd probably just have a quick look and check things manually by eye. However, if you want to make a genuine DRC I suggest you try out the KiCad Nightly development builds since KiCad 6 is not yet released.
I found this of KiCad 6 preview which shows the new &quot;Constraints&quot; pane (you have to scroll down a bit) that has a lot more detailed options for PCB restrictions:
https://techexplorations.com/blog/kicad/kicad-6-review-new-and-improved-features/