Dr Saya showed that 500 IU HCG only stays in your system for around 72 hours. 150 IU lasted 1 day.
The problem with this study is that the results are right at the limit of detectability—1 mIU/mL. If you take the 500 IU data and divide it by 3.333 (500/150), then add a little noise, the result is still consistent with the 150 IU data. I don't think the conclusion of a shorter duration for a smaller dose is justified by this alone.