It doesn't look like you are getting less when you have more from that picture though? I mean on that image it shows that you had 84k and got 9, then a bit over 85k and got 9 again and then some more and got 10 finally, then after that its purely higher and higher and constantly 10 because of that. I believe if you get more money on your account that means you are going to get more interest as well, quite simple math isn't it?

If you got like 90 and then get 9 sat but then 80k and got 10 that would be weird, that is what you are saying how did you get more sat when you have less money because that's not true at all and that's why you are getting an increased amount of money and that's the situation here. I can't say if it is this way or that way but that's about it and that's why I think you should not be worried about it at all and seems like you are getting what you should.