What is the meaning of A1778FCC on iPhone?

A1778 is one of Apple's model numbers for the iPhone 7.

FCC is the Federal Communications Commission in the USA.

(262502)

You do not say where you see this so it could be anything.

If a model number, perhaps this? --> iPhone 7 - Technical Specifications - Apple Support

It is a string of letters and numbers.

What is your actual question?