Sounds odd, that is a lot of oil you have had to put in. My 1.4 used to take approx. 3.5 litres of oil plus the molyslip at oil change c/w a new filter. It would always come up to level with that.
If you cannot find a leak, my thought is - are you certain it is the correct filter? But then, even a larger, more dense filter would be hard pressed to take an extra litre of oil. 2l can not a 4l can?
Edge 0-30 is good oil. I suppose all you can do is drain again, new filter, stick the oil back and see what happens.
Best of luck.