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The only way I can think of is by hiding the submit button preventing the user from submitting the form if the condition is not met. You can use the show/hide field option from the conditional logic feature. We need to create two conditions. One to hide the submit button if it's empty, and one to hide if it's filled but less than the minimum amount set. I cloned you form and see how it works by clicking this link,minimum value set is 23, if it's empty or below 23, you won't be able to submit. See how I did it below:
Please let us know if you need further help.
Sorry my bad, you can also do it by setting the setting the minimum value of the Number Field. Here's how:
You can do it 2 ways.
Hope this helps.