The 2 is irrelevant, the 4 determines whether you round up or down. since the four is less than 5 you round down. ( if the number to the right is 5 or greater you round up, if it is less than 5 you round down 0.142 = 0.100 = 0.1
if you have six possible outcomes for the first dice and you want it to roll 1 thru 4 then you have a four out of six chance and you have a 5 out of six chance for the second dice
