Steps to Reproduce:
Install JIRA Charting plugin.
Follow the plugin doccumentation
Add the Gadget.
Select the Period to "Yearly"
Set the "Days Previously" to 3000 and save.
Like the Bundled Gadget it will shows the graph based on year.
This warning appears "Days must not exceed 300 for daily period"
So far tested with "Time Since" gadget that bundled with JIRA, the error will follow its selected period. For example, selecting "weekly" will throws warning "Days must not exceed 1750 for weekly period"