Data usage too high after setting to lowest bit-rate

[Techquestions]

I've set my data rate to the lowest "data saver" setting which says is 24  kbit/s which the equivalent of roughly 10Mb per hour I have a data monitor installed and after about 3 hrs of listens it says Spotify has used 240Mb near 10 x more and around 180 kbit/s per hour and basically lossless, is there something I'm missing?