Hi Cesar
Greetings from Syncfusion.
Currently the support “Customizing Hint Label and Assistive Label font size” was not available and we have planned to implement this support for our upcoming Volume-1 release which will be rolled out on mid of March 2019. You can track the status of your request, review the proposed resolution timeline, and contact us for any further inquiries through this link. We appreciate your patience until then.
If you have any more specification/precise replication procedure or a scenario to be tested, you can add it as a comment in the portal link above.
Thanks,
Bharathiraja.