A 19.9% placement has to be within the end combined total of fully paid shares.
eg-- 19.9% of 1000 shares = 199shares
comb total = 1199 shares now 199 shares = @ 16.597%
Placement of 249 shares.
comb total = 1249 shares thus 249 shares = 19.9359%.
You can see how an error of 50 shares happens.
I can only deal in small numbers, hope this helps.