Joomla number Form Field Type
The number form field type provides a text box with stepper arrows to let the user increase and decrease the value using their mouse or by tapping with a fingertip. This field includes built-in validation to reject non-numerical entries.
XML Field Definition
<field name="mynumber"
type="number"
label="Choose an number"
min="0"
max="10"
step="1" />
This will create a number box with possibility to chose values between 0 and 10 and change current value by 1 each time user click up or down field button.
Additional Parameters
min: This value is the lowest that can be chosen.
max: This value is the highest that can be chosen.
step: If user click up or down arrow, current value will change by this attribute. The step default to 1.