every time i press bottles?

This is quite a general error so it depends how the button has been programmed. It may have been set as open price such as a department button. In that case, you would type a price first (no decimal point) so try typing 100 then press BOTTLES and see if it sells one for $1.

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If anyone needs more information, the Sam4s SPS2000 programming manual is here:

http://the-checkout-tech.com/manuals/cashregisters/Samsung3.php

Registerman
May 2012