945 to 1821 = 8.6h
Machine A : 1 h -> 67 bottles => 8.6 h = 67 x 8.6 = 576.2 ~ 576 bottles
Machine B : 1 h -> 43 bottles => 8.6 h = 43 x 8.6 = 369.8 ~ 369 bottles
Therefore total bottles produced in that period = 576 + 369 = 945 bottles
In reality, the machines will produce the bottles at the rate that they run and we cannot add up the bottles produced and get a round off as a fraction of a bottle cannot be produced. So to get an accurate number of bottles, we have to calculate the individual production of each machine due to the rounding error in summing them up.
The 0.2 and 0.8 cannot add up to make a bottle, it would be an odd-looking bottle?