Good evening. I gave my child vitamin D drops (Aquadetrim 15000 IU) and…

Good evening. I gave my child vitamin D drops (Aquadetrim 15000 IU) and decided to switch to another one. Yesterday I bought it and didn't look at how many IU were in it. Today when I gave it to my child, I saw that it was written 500 IU. The doctor prescribed us to give two drops each. But it turns out that in two drops there was 30000 IU before and now 1000. I don't quite understand how to give the new vitamin D. Has anyone switched to another vitamin D?