sink not flush with granite counter

Just had new granite counters installed.
We bought a new Kohler cast iron porcelain coated sink, drop in style.
The problem-- the edge of the sink is not flush with the counter.
It looks like the sink is warped. The opposite corners are 1/8 off.
For example if I press the right front corner down to touch the counter,
the left rear corner will have an 1/8" gap with the counter.

I checked the granite, it is level and flat.

I'm wondering if this is normal with cast iron sinks or is the sink defective.

They can be warped. It's not an exact science. You can try more sinks, or caulk the sink in as is, and decide which side is going to be up a little bit.
I would op for the front edge touching the granite, and the side away from you being up.
Or you can balance between the two sides. When it's caulked, it won't move.

They are fired until they are red hot, so they are more likely to be a bit warped than not. Once it is caulked in place it will NOT wiggle.

Thanks for the reply. I was thinking they are probably not perfect, but I wanted to make sure since it was a special order.
Didn't want to bring it back and wait three weeks only to find the next one is the same way or worse.