I don't see anything obviously wrong with the code.

The only thing I can think of is that the site you're using the bot with is setting the roll value to some bizarre value?

Maybe add a "print" statement in to debug what the value of lastBet.Roll actually is. It should output to the Bot's console window.
function dobet()
print("Roll: ", lastBet.Roll)
if (lasbetBet.Roll < 3.3 or lastBet.Roll > 96.7) then
chance = 49.1089
end
...