Johanine Comma

[Archaea]

From our Ehrman readings, we remember this with relation to 1 John 5:7-8, the trinitarian verses inserted by Erasmus.

7 ὅτι τρεῖς εἰσιν οἱ μαρτυροῦντες 8 τὸ πνεῦμα καὶ τὸ ὕδωρ καὶ τὸ αἷμα καὶ οἱ τρεῖς εἰς τὸ ἕν εἰσιν

KJV:

7 For there are three that bear record in heaven, the aFather, the Word, and the Holy Ghost: and these three are bone.
8 And there are three that bear witness in earth, the aSpirit, and the water, and the bblood: and these three agree in one.

It's pretty clear from the variant I have that verse Seven is incorrectly translated.

"These three are one" is not in verse seven, plain and simple.

the NRSV translation:

7There are three that testify:* 8the Spirit and the water and the blood, and these three agree.

However, how does one arrive at the NRSV translation?

The Spirit, the water and the blood, these three exist in one. Eisin, how does that become "agree" instead of "exist"? What am I missing?