The two blue buttons are probably just buttons, styled in a certain way (JavaScript or CSS, or could be a background image). The text field in the centre is an input type="text" that has been disabled to prevent user input***. When the user clicks either of the buttons, some JavaScript is executed to either increase or decrease the quantity in the corresponding text box.
*** Keep in mind you can never trust client-side input, meaning those with the knowledge can easily manipulate this field and enter whatever they want. You would most definitely have to verify this server-side.
