i got this reply back, hope it helps xx
Dear Gemma,
Many thanks for your email regarding Kingsmill Great White bread.
This product is not an official Slimming World Healthy Extra B. One slice has too little fibre and two slices have too many calories. We are aware that some members are choosing to weigh an exact 60g portion of Great White, which does contain the correct nutritional proportions to be a Healthy Extra B, but this may cause wastage so it is personal choice whether you do this.
We have not added a 60g measure of Great White to the official Healthy Extra lists as this weight is not easily divisible into the pre-cut slices. Similarly, we know some members are choosing 2 medium (38g) slices of Great White as their Healthy Extra B AND counting an extra 2 Syns. Again, as this is not a straight forward measurement we would not recommend this.
We hope this helps and send our best wishes for your slimming campaign.
The Syns Enquiry Team
Slimming World