Head over to the Format menu of the chart and click through the Abbreviate thousands and millions option. Choose a particular abbreviation such as Thousands, Millions, Billions and Trillions. The Auto abbreviation is selected by default.
Please note that if you choose the level of abbreviation higher than value, it won’t be abbreviated (e.g. if you choose Billions abbreviation for 1,000,000, it won’t be abbreviated to 0.001B).
Here are the abbreviations:
1 000 – Thousands k
1 000 000 – Millions M
1 000 000 000 – Billions B
1 000 000 000 000 – Trillions Tr
1 000 000 000 000 000 Quadrillions Q