Rabbit dosage is the same as the dosage used for cats (which is half the dogs dosage)
Works out to 1 drop of metacam per lb of bunny.
Your friends bunn should be getting 6 drops of metacam.
Sadly its been awhile and I cant remember how many drops per ml, but that 0.6ml isnt correct, its some wierd number.
Easiest thing to do would be to get a syringe, put 7, yes 7 drops of metacam into the lid of the syringe and suck all those up into the syringe and give them to the bunny. The extra drop is to take the room in the tip of the syringe that doesn't get squished out.