How can we even begin to guess if you have not bothered to tell us what you have? Argos lists a dozen or more different "Weight Watchers Scales" - and none of them are blenders, which is the category under which you posted.
Or is it a food scale?
http://www.weightwatchers.com/images/1033/dynamic/GCMSImages/1108-USA-revised_booklet_artwork-2010.6.18.pdf (Read page 4)
http://www.weightwatchers.com/images/1033/dynamic/GCMSImages/ElectronicScale_Quick%20Start.pdf
https://www.weightwatchers.co.uk/images/2057/dynamic/GCMSImages/Kitchen_POINTS_Scales_Interactive_User_Guide.pdf (Read Page 7)
https://www.youtube.com/watch?v=T27M_TaKKoE
https://www.youtube.com/watch?v=FbkgR8RTfBI
Acp
August 2017