Calories labels and variability
don't believe the label
Variability is everywhere. And food labeling is notorious for it. Some loaves of bread are uniformly cut. In some others, the size of the loaf starts small and becomes larger at the other end.
In the second case, when I inspected the calorie label, it said 2 slices were 190 calories (for 60 gms). I wasn’t sure how many calories it was so ended up weighing the two slices. The two smallest-sized slices were exactly 60 gms. And the later larger slices were in the 80-93 gms range for two slices. That would put two slices in the nearly 300-calorie range.
There is a huge range of variation and variability in food product labeling. Portion sizes vary from brand to brand. The right way would be to measure them to be more accurate. However, even with this, in many cases, there is gross mislabeling, rounding off of calories per serving size (since it is allowed), and underreporting of sugar, carbs, protein, and fat (since rounding down is allowed) with legally manipulated irregularities abound.
So buyer beware. And eater beware. In most cases, a small serving size leads to a large number of calories in prepared form (cereals, hot drinks, and others have added recommendations for milk or whiteners and these add up to a lot)