Why there is amount difference between writ surveys?

seesonchanrwb17_ESO

For example, sometimes the enchant survey in orsinium will be 6 nodes, or 7 nodes. But the cloth and ore one is normally 8 nodes.
Why is that?
@ZOS_GinaBruno

Faunter

I don't know, but I liked it better in Craglorn where all the surveys had 8 nodes. I often find myself double-checking the survey area before I leave it in Wrothgar to make sure I didn't miss anything, as there is no way of knowing which survey reports have how many nodes without experience.