The type checks for open answers (e.g. integer, point number, e-mail addresses ) are executed by a browser-specific validation. This check cannot be edited using the plausibility check editor, and neither is it displayed in the questionnaire overview. The language of the messages therefore depends on the language version of the browser and can only be changed there.
The type check function can be found in the following question types with open input fields:
111 (single selection next to each other) with other field, 121 (multiple selection next to each other) with other field, 311 (standard matrix) with other field and question types for open questions with single-line text fields (141, 143 and 144).