I downloaded the trial. I have no idea how the scoring works. In the trial version, they have a 5 minute thing. I have no idea how long it took to get scores that high.
I think the highest score I got in the 5 minute demo was 30 something thousand. I think I got a x24 chain once. I usually get a x13 chain with all three of a kinds. I'm so used to playing Tetris Attack that it's so hard for me to look for straights and flushes.