Hi Naveen,
Thank you for reaching out!
When more than 15 appointments are scheduled on the same day, they will render as shown in the screenshot you provided. This is the expected behavior. In such cases, you can enable the tooltip to view the appointment details. Please refer to the user guide and demo linked below for more information on tooltip functionality.
https://ej2.syncfusion.com/documentation/schedule/appointments#display-tooltip-for-appointments
https://ej2.syncfusion.com/demos/#/tailwind3/schedule/tooltip.html