Iksan : seu
Iksā : você é
Issa : é / he
Iksi : somos
Iksāt : vocês são
Issi : são

Iksā is like "you are" for one guy, and iksāt is like "you guys are" for multiple people.

Because it is in second person plural :) In english we can use "you are" both for singular and for plural. But in high valyrian it is two different words :)