Oil leak

[Gzetero]

My GZ250 is leaking oil, the leakage is small, it is not noticeable on the floor where I park the bike (no drops) but you can see oil around the cylinder (attached pics), nevertheless I would like to know your opinion on when I should start to get worried about the leakage being to much. I check the engine oil every time I ride so I am not too worried about the motorcycle having a low level of oil.

I will appreciate any advice you can provide.

Thanks.