I believe the label shows the quantity of each deworming substance, Praziquantel , Pyrantel,and Albendazole, in 100 ml of product. If you divide these number by 100, you will know how much is in 1ml of product ; to know how much is in the 15 ml bottle, divide by 6.6666.
But you must start by calculating how much mg of each substance you need for each individual chick.
Are you able to do the calculation with the links provided, or do you need help ?
I have used Praziquantel for two of my adult chickens and it was extremely effective with a slightly lower dosage than the one given by so I would dose conservatively or like others have said give two lower doses a week apart.
As for the role of the excipient, I also don't have access where I live to approved poultry meds. When my vets prescribes medications meant for humans or other animals, she says it doesn't matter what the excipient is and that I can either syringe it directly or mix it with scrambled egg. In your case it would better to dose each chick individually either in a tiny amount of food or with a syringe to be sure they get enough.
I didn't see if you mentioned in what form the product came. If it's a gel that doesn't mix well in water, mix it like you would do a mayonnaise, putting the medication in first, then adding and mixing very small amount of water in.
At one point, I was in a desperate situation to get a dewormer that worked for tapeworms and did not require a prescription where I live, so I ordered Worm-out gel from jedds.com. It took only a week to ship from the US to France but I had to pay tax so it was expensive. It's extremely convenient because it's possible either to dilute it in water for the whole flock or to be given with a syringe individually. But in your case I probably would not wait a whole week.