Arcane Shield glich

According to the direction in the game, Arcane Shield should have 500 HP at least

and should have MORE HP with the 1st upgrade
(can somebody tell how much it should have exactly?)


After I tested it both with/without armor and pet

I found it seems to absorb around ONLY 400 damage before it breaks

charging doesn't affect the amount
(To dev: why no extra HP for charging?)


PS:
1. I have the 1st upgrade of the shield
2. I've only tested this in elite PvE
3. shield seems to absorb lesser if I equip armor



Can someone confirm this?