Ml5 g/box on a xant, have I got it wrong?

[Zoolog]

I'm in the middle of a xantia thrust bearing /clutch change. It's a 2.0 hdi 110 so it's got the ml5 box. I have a terrible feeling that I've put the offside seal in back to front. It's a dealer supplied seal but it differed from the original in that it didn't have a flange. Am I right wrong and most importantly does it matter?