SVC meaning

You used a 3rd party site to check; SVC means whatever that site defines it as. If it’s a replacement phone that means that Apple “fixed” the original phone by replacing it. The model number is more useful. But given that it was a “service replacement” SVC probably means just that.

Here’s something to think about whenever you buy a used Apple product→The All Too Common SAD Reality of Buying a Used iPad/iPhone

Where are you buying this from? If you're purchasing a second-hand iPhone, you need to ensure that the seller removes the activation lock, otherwise you'll be buying a brick. For security reasons, only the original owner can deactivate an iPhone or iPad. Please ask the seller if they've removed the lock - and get photographical evidence, don't just take their word for it. Ask them to send you a screenshot of their Apple ID account to prove the phone is no longer registered to them.

As you probably know, N means its a service replacement, confirming what you were told. It might be new or might be refurbished; there’s no easy way to tell.

The important thing is to know the seller and have a way to stay in touch with the seller if you have any issues with the phone.

Where exactly are you seeing this? Can you put this into a little more context, such as a screenshot of were you are seeing this?