Refer it, Power BI chooses the best tick interval based on your data range, and creates a minimal format string for this unit interval, to preserve space.
Unfortunately, power bi does not support custom y-axis intervals at this time. If you would like to suggest feature improvements, you may vote the idea and comment here to improve this feature. It is a place for customers provide feedback about Microsoft Office products . What’s more, if a feedback is high voted there by other customers, it will be promising that Microsoft Product Team will take it into consideration when designing the next version in the future.
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