"Hi" means the share hash has high - which means the difficulty value was low.
I posted an explanation of "hi" vs "low" before, so I wont repeat that, but basically your miner sent a bunch of shares with the difficulty below what the pool asked for.
e.g. if the pool says send me 4098 diff shares and your miner sends 410 diff shares, then they are "hi" and rejected.

Firstly, it makes no difference to your reward, since e.g. on average one in every 10 of your 410 diff shares would be above 4098 so you expect to get the same reward.

Secondly, you'd need to check both numbers under "hi" to make proper sense of it.
You probably sent a whole bunch of low diff shares when your miner connected, but the value of those shares probably doesn't add up to much.
The "hi" value will say V/N where V = total value of the shares and N = the number of shares.
As always, it's the value V that actually matters, but if you are sending truck loads of them (high N) then it's probably Bitmain strikes again
Although Bitmain can build miners, their programmers are crap.

Cannan on the other hand Well their top guy setup the OpenWrt OS and wrote the web interface in the first Avalon miner that Bitmain copied directly into their first S1 miner.
He also wrote the first version of the Icarus and Avalon driver in cgminer.
Avalon also had the first ASIC miner - so yeah there are a few more reasons why I think Canaan is better than Bitmain.
Pity their prices were/are high - that's a strike against them IMO - market forces ... the force of many sheeple Hopefully it will go back down ...
Though they did the same with the first Avalon miner ... so it's not unexpected ... and I trashed them back then also