The vet gave the correct dosing for Safeguard Goat Wormer in his first sentence, and then followed up with dosing for Safeguard Aquasol, which is what he used.
Safeguard Goat wormer contains 100 mg/ml of medication, Aquasol contains 200 mg/ml of medication.
When discussing dosing, one should be very clear on what medication, form and % of medication they are talking about. Dosing in volume (ml) will be different for each of those medications based on concentration of the medication (mg) in each ml of it. How many mg of medication are in each ml of the liquid is what is important, so that the appropriate amount is given. If the aquasol is mixed in drinking water, the dose will also be different as it's diluted and based on the average intake of drinking water each day. When given directly orally, the dose is not spread out through the day, it's given all at once. All of those variables matter.