It should default to the current post ID, if ACF can figure out what the current post ID is.
First is tries get_the_ID(), then it tries get_queried_object(). It it can’t figure out the post ID then it defaults to “options”
You can test what ACF is getting by calling the function.
$post_id = acf_get_valid_post_id();
echo $post_id;
It really depends on where you’re trying to put the form.
