Bought a new pre-seasoned cast iron and not sure if seasoning is good Noob on cast iron skillets here.

I've been in love with this type of cooking for a while and just bought yesterday on amazon my first skillet.

It's not a Lodge but a Utopian Kitchen (Chinese manufacturer).

I've used it yesterday for the first time and since it's pre-seasoned I didn't do anything before usage, just a quick wash with cold water.

I've noticed that on the first heating a circle in the skillet appeared. And it's still visible today after cooking some meat yesterday.

I'm not sure if the "circle" means that the pre-seasoning is not "well-done".
By looking at other questions here, a common practice is to season again the skillet.

Is it what I should do in my case?
What are the parameters to evaluate if a seasoning is good or bad?
I've seen similar things on a couple of pre-seasoned pans (one of them a Lodge). My suspicion is that the uneven heating of the pan leads the seasoning in one area to burn, while the other area completes the polymerization that began during pre-seasoning. 

The number one thing that people do wrong with cast iron is worrying too much about the seasoning. Seasoning will basically just happen eventually; manually seasoning the pan is just an optional means to shortcut a longer period of natural seasoning through cooking; actual problems with the surface (rust, caked-on carbon, and... I think that's it) are thoroughly obvious.

Seasoning is as seasoning does. A cast-iron pan will never be as non-stick as a teflon-coated pan, but it should display superior food release compared to a bare steel pan. So just... cook with the thing. Differences in shininess should be ignored; differences in stickiness should not be.