MacBook Pro's serial number: What's the difference between C02... and FVF...?

I'm intend to buy a MacBook Pro 2017 13inch 2017 non-touchbar 128Gb SSD (model MPXQ2/MPXR2). I found that almost of these have the serial number start with C02... but some start with FVF...

So what's the difference between 2 kind of serial number?

Thank all!