Hi. i bought a plate of borosilicate glass. but when i put it on my table top the glass is not level. when i have it on the table 3 of the corners is on the tabletop. but the last corner of the borosilicate is 1mm over the table top.
if i turn the borosilicate plat1e. the problem is at the same corner all the time.

have tried to place it on a mirror and living room windows. but the borosilicate glass has a gap in one corner of 1mm.

is this normal?

No. You have a bad piece of glass.

I second that. Get new glass.