Average item level

I had the following equipment on my character:

Kintoki (item level 170)

Sky Pirate's Helm of Fending (item level 185)
Sky Pirate's Coat of Fending (item level 185)
Sky Pirate's Gauntlets of Fending (item level 185)
Yasha Kawa-obi of Fending (item level 170)
Sky Pirate's Gaskins of Fending (item level 185)
Yasha Sune-ate of Fending (item level 170)

Yasha Necklace of Fending (item level 170)
Yasha Earring of Fending (item level 170)
Yasha Bracelets of Slaying (item level 170)
Yasha Ring of Fending (item level 170)
Yasha Ring of Slaying (item level 170)

The average item level supposed to be precisely 175, not more not less, without rounding up or down. But the game shows me 174.

Why so?

What about shield?

/10chars

2H weapons get counted twice, so do other item pieces that take up two slots like cloaks. Add up all numbers, divide by 13, round down. 2270/13 = 174.xxx = 174