Question S/N Not Matching on Android Phone

Hi all,

I have recently bought a dual sim phone and I noticed that, although the imei numbers on the box, in the phone and in the Android info match, the serial number doesn't.

On the box and inside the phone, under the battery, the number is the same, but when I read it in the Android phone info, there is a totally different number.

What does it mean? Have I been swindled?

Thank you,