Question about k14 gunsight?

Hi everybody I have a question about the k14 gunsight used on p51d. I didn't understand how it works. I mean there are 6 diamond that draw an imaginary circle and a dot, then I saw that there is also a little cross. When diamonds surround the enemy airplane with the dot in the middle ( of course the wing span must be correct) can I shoot or I have to wait that the dot overlaps the small cross?

Please answer without explaining what is the k14 just answer the question

Thanks