Minimum value

We have integrated a simple calculation into Contact Form 7 with your plugin. You enter a number, it is multiplied by a certain amount in the background and you get the result. The problem is that unfortunately the result can only start from the number 150, no matter what number you enter. For example, multiply by the number 3. If you enter less than 50, the result is less than 150, which is not supposed to be the case. Nevertheless, it must still be possible to enter numbers smaller than 50, but here the result would always be 150, and the result only changes once you enter 51. I hope you understand what I mean? Is there a solution for this?