Can someone please explain creating encounters to me?

So if I understand it correctly the total of all of the npcs’ level in an easy encounter should be: total of NPC’s level divided by 2.

Most examples in the core rules follow this rule but I’ve seen enough contradictions to be confused.
Can someone please explain this example in core rules:
“Imagine you are planning an easy encounter for a group of 6 1st level characters, fighting a horde of goblins. Your NPC level budget would only allow you to include six 1st level NPCs."

Shouldn’t it be 3 1st level NPCs? Following the rule: Encounter difficulty Easy = Total Party Level x.5

That is under:

which is different from normal NPCs.

If you read the paragraph directly above/before the one you quoted:

When designing an encounter, you may want to designate some enemies as minions, or easily dispensable grunts that still pose a threat to the party. You can trade any NPC for three minions of the same level. Minions have the same stats as any other enemy NPC of their level, but their hit points are divided by four.

Now, you are correct in that it should be 3, not 6 (and then 9 not 18). It was either suppose to say “moderate” there, or the numbers are wrong.

Also, remember, these are guidelines and suggestions. So many variables with feats, boons and banes, what looks like a moderate encounter can quickly become easy.

And player ingenuity can always throuw things out the door, not to mention explosions and bad rolls.

As you build more and more encounters, you will start to just get a natural feel for them.

Start off with what it says if you haven’t done anything before, and you’ll get more comfortable.

For example, that 6v6 vs 3v6 isn’t going to be too huge for 1st level characters, but I might come from a harder mindset, where what is called moderate I consider to be easy in a lot of cases.