The step attribute is for this. Your code now has the value any, which means that any values are accepted and the step size is the default, 1. Replace it by a specific number to set the granularity and the step size. Example:
<input type="number" step="0.00000001" value="0.00000000">Note: The end tag </input> is invalid in HTML syntax for HTML5. In XHTML syntax it is allowed, but “self-closing tags” are recommended instead of it, e.g. <input type="number" step="0.00000001" value="0.00000000" />.