Annotation:
In Japan, the same size (1/4? loaf) of bread is sold sliced at different thicknesses.
That's what this sentence is referring to.
Perhaps the most common are 6 and 8.
4, 5 and 10 are also seen.
10 is similar to the thickness of the average slice in the USA.
Here are some example images.
6-slice
https://www.amazon.co.jp/exec/o...ocmanmaru1-22/
5-slice
https://www.amazon.co.jp/%E8%B6...0CE45YVK&psc=1