Hello everyone, please check this

Recently on july6th 2018
I have undergone my F1 Visa interview

The visa officer after few questions he said everything was fine from your side but due to some technical errors (SEVIS HIT), you have to wait for few days
He hold my passport and gave 221g form with "SEVIS HIT comment on it.
If anybody know about this please help me, like what does "SEVIS HIT" means. How many days it make to resolve ?

Any idea about it please tell me
And today my case last updated was changed from 6th july to 12th july

Thank you