Is this SN plan ok?

[thekulprit]

Hi all. I have found a source for SN but dont have all the requirements for anti vomiting drug. I just have olanzapine that i read can be used for nausea and vomiting. I can take ibuprofen and paracetamol. I dont have a scales so plan on cutting up a quarter of a 100g package by eye. Is that ok or does it have to be exactly 25g? Thanks