You can find the character limit option only in single-line text and long text fields (without rich text). To enable it in the form:

💡This option doesn't appear if a field is a long text with rich-text enabled.

You might wanna hide the characters remaining. Especially if you want to limit very long submissions, but not have users feel like this is some kind of ‘target’ count.

In this case, you could simply use Regex field validation instead of the built-in character count function. Here’s how to set it up:
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^.{1,10}$

This pattern matches a single-line value containing 1 to 10 characters, inclusive. It does not match an empty value or text containing line breaks. For text that may contain line breaks, use ^[\s\S]{1,10}$ instead. Adjust the numbers to set the range you need. For this pattern, use an error message such as “Enter 1–10 characters”; the screenshot’s “less than 10” wording is imprecise.

Here’s how the form looks to the end user:

The error message appears when the entered value does not match the validation rule.