You can set the Max characters to any number you would like as long as it is less than or equal to the available characters in that field’s data type.
Styling the Field Help
The remaining characters text is considered “Field Help” and is customizable using the Style Wizard. In the Caspio Explorer window, go to the Styles view. Select the Style you are using for your DataPage and click Edit. Proceed to the Settings screen. Under the Forms/Details group, locate the Fields subheading. Field Help is the third Element Type. You can use the controls to change the font style and layout of that help field.