Format of Y-axis on Page CTR within AdSense chart is incorrect

## Bug Description

On a site with AdSense connected but has zero revenue, the chart for the Y axis of the Page CTR shows data formatted as 2,000%, 4000%, etc. When a site has data, the format is correct, i.e., 10%. It's only a minor issue, but I feel the format of the Y-axis on zero data should be the same as a site with AdSense revenue.

You can see the two screenshots below for an example:

Site with AdSense revenue


Site with no AdSense revenue


## Steps to reproduce

1. Set up AdSense on a site that has zero data.
2. Go to the chart on the dashboard and click on the Page CTR tab
3. Observe the Y-axis format, i.e 2,000%

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## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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Reproduce the issue by opening the AdSense chart for a site with zero revenue and selecting the Page CTR tab, then compare its Y-axis labels with a site that has revenue. Locate the Page CTR chart entry point and update the formatting so zero-data percentages match the normal display; verify both scenarios manually.

Written by the indexing model from the issue text.