For example for french fries, when the recipe calls for a mixture of
oil by 93% beef tallow and 7% cottonseed oil, I am not really sure do
they refer to percent of volume or weight. Please help me with this.
Thanks.

P.S. a mixture of oil is here just for the sake of an example, I know
it's not very healthy, but I mean I don't know what they are
refferring to, for any mixture for cooking in percents.