Yes, 一两,二两 is the standard way for inkstick weight. This should be 30g, 60g. On our website, we just listed it as S, M, L so that it could be easier for people to know the size easier. S is 30g, 一两; M 60g, 二两.
As for the weight you have mentioned, it does not always accurately match the 30g, 60g, etc. This is because the fresh ink weighs more than ‘older’ inks due to losing moisture contained in inkstick. This is getting so obvious when you look at Old Hu Kai Wen inksticks which are 20 years old and you will find the inkstick weighs so much lighter than freshly-made inkstick. 🙂
Yes, how to mark the weight clearly is very important. We have decided to edit our weight system on inkston.com for inksticks.
🙂 I hope this is helpful! And thanks a lot for pointing out this problem.