Even the number of letters in the name of the painting is relevant.
The challenge for Serge is to make it so inconspicuous that the main objective, which is the story and composition, does not suffer. If you ask him to explain, he will smile, and answer, “I will just say that in my compositions you will always see an odd number of flowers, even for a very large compositions. The number of floral elements in the composition plays a significant role in many cultures, including Russian and Japanese cultures, which I studied as an Ikebana artist. I do believe in the power of numbers, and have my lucky ones, but absolutely don't believe in ‘numerology,’ which takes it to absurdity.”
As far as "how does he do that"? He considers it a challenge and his secret — how to create a balanced, yet dynamic, composition and make sure that it has the right amount of elements in it.