Why the odd measurements of some of the dry ingredients?

The kind author of the recipe was no doubt trying to share the recipe with a population which does not tend to weigh ingredients. Those who normally use a metric measure are also often somewhat mystified by our use of the "cup" measure for both liquid and solid items. I believe with a little effort, you could reverse the conversion and reveal that most likely the flour should be 340 grams. The recipe was provided to you for free, out of the kindness of the author's heart. Perhaps a little gratitude is in order, rather than fault finding in the system of measures.

The recipe poster is located in the UK which converted to metric decades ago.
Her original recipe was probably in a mixture of grams (weight) and cups or spoons (volume).
A guess - she converted the grams to ounces for convenience of those in countries without metric.
Suggestions: either use the oz as given, if you have a scale, or convert back to metric (oz = 28g).