How do glyph calculations work?

jmmonnat_ESO

I made two level 12 pieces of heavy armor (gloves and leggings, I think it was) one after the other. I bought two of the same armor glyph of +12 health. Neither armor piece was improved... straight off the anvil.
When I enchanted the armor pieces, the leggings were +12 health, but the gloves were only +4 health. My skill was the same. The armor piece levels were the same. The glyphs were the same. The only thing different was the piece of armor.
Are there caps on how much you can glyph a particular piece of armor? Do you get the full amount for chest and legs and less for the other bits? If so, why didn't anyone tell us this?

SexyVette07

Gloves, boots, and belt all receive reduced benefits since they are considered lesser pieces.

Natjur

Its 40% on the lesser pieces, so you really got 4.8 health but I guess it rounds down

Tabia

I think shoulder armor is also reduced. Full enchantment on chest, legs and helmet.

Demli

Shield also gets full enchantment effect.