The text on your website is not legible on every type of device.
The font size has either not been configured correctly and is hard for a customer to read your content on any device. In order to create a good experience for the customer, you need to ensure your font size is legible on all types of devices.
Your web developer can help to set up the viewport correctly and then the correct font size so that it is legible on all types of devices. The font size should be set based on pixels but may need to be adjusted for different font types. The default font size is 16px (CSS pixels) and provides a good starting point.