If the forks are back in the bike, try to get them as vertical as possible take the tops off. mark the air gap you want in the forks - on the tube attached to the syringe, Say 74mm (iirc). then over fill fork with oil and pump to remove all air then push the tube into the fork till you get to the mark and suck out any excess oil. This way you have the exact same air gap either side.
Does that make sence? If not i will try to get some pics.

Ok. I had difficulty removing the fork tops and ended up removing the forks, but I will have a go. Do you think I need to if I have 450ml n each leg? Cheers!!

If everything was clean and oil free when you put everything back together, and your riding onthe road - i doubt you would notice a small difference between the 2 forks. Have you ridden the bike yet? If not, go for a spin and see. If it feels okay/fine then leave it be.