A Level Biology EQ

Hey guys, I was struggling with this question:
Scientists have found the mean length of time spent by onion cells in anaphase of mitosis is 105 minutes. They also found the cell cycle of cells in the onion root shown in Figure 2 takes 1080 minutes.
32 whole cells are shown in Figure 2.
Use this information and Figure 2 to calculate the length of time the cells of this onion root are in anaphase and then calculate the percentage difference between your answer and the mean length of time found by the scientists.
Figure 2 shows the cells the student saw in one field of view. He used this field of view to calculate the length of time these onion cells spent in anaphase of mitosis
And I found an answer which I understood up until they multiplied by 1080 minutes. Can anyone tell my why they do this?
They are working out the actual amount of time spent. I did this in a mock, attach a picture and then people will be able to help
num of cells in anaphase/32 * 1080 = mins of anaphase

then calc the difference and divide by 105 and * 100 to get the %