Can Someone Help Me Understand How Lichess Ratings Work?

I know we have a few online chess players here on HN. So this seems as good a place as any to ask.

I just can't fathom how the Lichess ratings system works at all. I know the theory behind such things; more points gained for beating higher rated opponents than lesser rated ones. Less points lost for losing to higher rated opponents than lesser rated ones, etc.

But, as I'm playing games on the site, the points I'm having awarded for wins or losses seem almost completely arbitrary... apart from never seeming to do me any favours. A couple of examples to illustrate:

1: I played a game against an opponent ranked 70 points above me. I won. S/he lost 7 points. I only gained 7.

2: I played a game against someone ranked 74 points above me. I lost. I lost 5 points. S/he gained 11.

3: I played an opponent rated 7 above me. I lost. I lost 5 points. S/he gained 54 points.

4: I played an opponent rated 13 above me. I won. I gained 6 points. S/he lost 5.

5: I played an opponent ranked 63 above me. I won. I gained 7 points. S/he lost 23

6: I played an opponent ranked 3 below me. I lost. I lost 5 points. S/he gained 30.

[BTW None of these games involved people with '?' after their ranking, which indicates it's not averaged out yet and is subject to huge swings]

So why the huge discrepancies and inconsistencies?

It seems that I never gain more than about 6 or 7 points, even if I beat someone with a far higher ranking than myself. Yet whenever someone on around the same level as me beats me, they sometimes gain 30 or 40 points.

Can anyone explain it to me?