Need help with understanding dosing - I feel like I'm missing something!

Hello! I know that there are so many questions about dosage and units all the time on this sub but I am just really confused and I just need some help. Can someone please explain to me very simply if this is correct? I tried looking the information up online and I am even more confused.

I am currently on 4.5mg of compounded tirzepatide and I have finally decided to move up in dose. My doctor sent in the prescription but I feel like it doesn't look right. This is what I am currently on for roughly a 3 month vial:

Tirzepatide/Pyridoxine 15mg-4mg/0.5mL MDV (2mL 60mg) (It says to draw 15 units)

The new script for 5.5 says this:

Tirzepatide/Pyridoxine 15mg-4mg/0.5mL MDV (2mL 60mg) (It says to draw 18 units)

Is this right? The unit amount is the number on the syringe that I draw right?? I just want to make sure going forward and spending the money. The doctor is pretty new at this and has made mistakes sending in my prescription before. Again, I'm really sorry for asking a dumb question but I'm just so confused and not the best as math. Thank you!