To fix the issue with the numpad shifting on the POS screen, you can try disabling the responsive behavior of the screen. This can be done by adding the following CSS code to your POS screen:

.o_touch_container {
        width: auto !important;
    }

This will prevent the POS screen from adjusting its width based on the screen size, and the numpad should remain in one position when typing in the figures.

Note: this solution may not work if you are using a custom POS screen that has a different structure than the default POS screen in Odoo. In that case, you may need to adjust the CSS code to target the correct elements on your custom POS screen.