I have posted the scale for conversion from 1/8s and 1/4s to grammes for those who need it.

1/8 of an ounce is exactly 3.5 grammes
1/4 = 7 grammes
1/2 = 14 grammes
1oz = 28 grammes

Thats it, simple really, so if somebody is selling you an 1/8th that weighs less than 3.5 you are being ripped off.

This is not opinion but FACT.

Therefore your half an eigth should have weighed in at 1.75 grammes