In "The Rules of the Game," when did Waverly start playing chess?

We are told that Waverly's family receives the chess set
when they went to the annual Christmas party held at the First Chinese Baptist Church.
There was a Santa there with a sack of presents, and it is when Waverly goes to Santa to
receive her present that we find out how old she was. Note how the narration gives yet
one more example of the complex, hybrid world that Waverly inhabits, for she is not sure
how to answer the question:

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When my turn came up, the Santa man asked me how
old I was. I thought it was a trick question; I was seven according to the American
formula and eight by the Chinese calendar. I said I was born on March 17, 1951. That
seemed to satisfy him.

This
clearly shows how confusing the position of someone like Waverly is when you belong to
two different worlds but aren't sure of how to position
yourself.

However, even though it is Waverly's older
brother Vincent who gets the chess set, it is when Waverly was seven (according to the
American formula) that she started to learn how to play chess.