Mobile Formatting Issue

Nothing is broken, it is just the way the thing is coded.
You could try putting a media query into your css.

Maybe something like

/* Smartphones (portrait and landscape) ----------- */
    @media only screen
    and (min-device-width : 320px)
    and (max-device-width : 480px) {

    /* Styles */
._dgx_donate_amount {clear:both;}
    }