contains only samples within ... percent of normal

contains only samples within … percent of normal is used to identify cases for which the elements of a group are all within the normal range, with some percentage tolerance.

For example, if the group food contains egg, milk and soy, then the case

egg            22 [5 - 15]            8 [5 - 15]          18 [5 - 15]
milk           24 [

satisfies the condition

food contains only samples within 20 percent of normal

It’s also possible to use the “%” symbol:

food contains only samples within 20 % of normal