Too much oil?

I refilled a '91 5 speed gearbox recently, before seeing the posts on capacities.  It took 3 litres before I could feel the oil level reach the top with my finger.  I think this was because I had jacked up the front of the car just enough to slide under to remove the gearbox plugs which allowed the extra oil to pool at the end of the box.  I see its supposed to take only 2 litres.  Now do I need to jack it up again, get back under the car, remove the overflow plug, unjack the car, let the surplus drain out, rejack the car and replace the plug, or can I just drive it with the extra litre in?  I dont want to damage the seals obviously, but if I can avoid the above, great!..
Thanks
Mark
 

 I’m no expert, but in my mind if it needs 2 litres, then it needs 2 litres - not 3 litres.
I’d be inclined to get it back to where it should be.

 Mark, ideally the car should be up on ramps/axle stands when you do the gearbox or diff levels. I hope you had axle stands when you went underneath and didn’t rely on the jack?

For sure Geoff, I may be lazy but Im not stupid!! 
Oh well back under I go…! flip its so hot in the garage, im perspiring just thinking about it…
Cheers
Mark