Question on time-weighted rates of return – dividend timing

I am confused by the way they include dividend payment in the calculation. Based on the example, there are two periods which is 1 jan – 31 april and then second period from 1 may – 31 dec. If they do not take the final value as 132 million in the first Holding Period Return calculation which occurs on the 1st of May, why do they include the 2 million dividend in the calculation since the dividend comes in on the same day as when investors decided to increase their investment?