Looking at your code... the only time it will end up as chance=49 is when the lastBet.Roll was <3.3 or > 96.7 AND it was a loss...

The "if !win then... else..." block you have means that if it was a win... it sets nextbet = balance /1024 and then chance is set to 97.2549.

So currently, will only work if it is < 3.3... as you're betting "high" to start by default, if the roll is over 96.7 you'll win and the chance won't change.