How much chlorine to shock at open?

[JohnT]

Each gallon will add about 3ppm to your pool, so you probably got in the neighborhood of 24ppm. Should be fine.

[CarlD]

No one can tell with out test levels. Get yourself a FAS-DPD test kit ASAP.
It can be the Taylor K2006 or K2006C
It can be the TroubleFreePools Kit.
It can be the Leslies FAS-DPD Service Test Kit.

You spent all that money on a concrete pool with an SWG--the $60 to $80 on the FAS-DPD test kit will be the BEST money you ever spent.

And kick an extra 20-30 bucks for a salt-level test kit--with an SWG it will give you better info than the strips they give with the unit.

The idea of shocking is to kill what ever it growing AND break down the resulting CC (combined chloramines) so your pool is clear and sweet.

Without FC, CC and CYA levels it's impossible to tell if you have added enough bleach.

You CAN have a pool store test the water for you--but don't be talked into buying the slew of useless chemicals they'll push on you--phosphate remover is the latest snake oil.