What is the use of step attribute in <input> tag?

Question

Example from a quiz question:

<input type="number" name="values"
min="0" max="30" step="7" value="0">

Please explain me this code and also about these combinations:
14, 0, 28, 7, 17
0, 21, 7, 28, 14
7, 23, 14, 0, 28
30, 0, 7, 28, 14

Why was second one the right answer?

Answer 1

when you have input type number, on the input field in the right you have 2 arrows - to increase and to decrease. and the step means how big should the increase or decrease be. So for example if you set the step to 5 you increase the number by 5 -- 0,5,10,15,20...

Answer 2

Thanks Proff

Answer 3

Profesionals use Tk library for C#,C++,python,java and step +- aren't problem