This is not quite correct. Fractions are not dropped or rounded off; they are retained (A7.2). You use the rightmost column of the IFT whose listed FP does not exceed the total adjusted FP of the attack. Any excess FP factors have no effect. (A7.3)
So, a total adjusted FP of 1/2 uses the rightmost column which does not exceed the total adjusted FP. 1FP exceeds 1/2FP so no column, no effect (or you use the implied 0FP column which equals no FP, so no effect.)
Also, when you Cower, you shift columns, you don't half FP. 1FP shifts to the left off the chart. (A7.9)