Average item Lv Formula?

[Ri_ri]

I don't have screen shots now because I am on notebook.

Full DL (item level 70 on all slots) + regular relic (item level 80 weapon) = average item level 71.
With full DL + Garuda Van + Ultima ring (item level 80 accessory) = average item level 70.

In total, both setups have the same numbers, but the one with the relic gets a higher average item level, so I think slots do have different weight. I'll test this better later.

Edit: no I won't. I'm horrible at math and I hate this average item level thing