Okay, too much "basic" info here. It's actually more complicated than this. There's a reason why it's confusing.
There are two factors that are at work here:
1) if the lyophilized HCG product comes in an ampule or vial
2) if the solvent contains benzyl alcohol
If the HCG product comes in an amp, and the solvent does not contain BA, you're looking at 9 days max.
If the HCG product comes in an amp, and the solvent does have BA (usually slightly under 1%), then you are looking at about 30 days.
If the HCG product comes in a sterile vial, and reconstitution is performed in the vial, and the solvent does NOT contain BA, you're looking about 20-30 days.
If the HCG product comes in a sterile vial, and reconstitution is performed in the vial, and the solvent DOES contain BA, you're looking about 60 days.
If the HCG is vials, the only way to maintain the 60 days is by drawing the sterile air from the HCG vial, injecting that into the solvent, drawing the solvent, and injecting into the HCG vial. This keeps the process as sterile as possible, allowing the 60 day expiry.
Depending on the brand AND place of manufacturer, the solvent (typically sodium chloride) may or may not have BA. Generally, the small unit amp solvents do NOT contain BA - the BA adds some bite to the injection, so small unit preparations (not the larger vials) don't contain it since the intention is to use all of it immediately.
The end result is - buy some BAC water so you know. Cheap and effective.