My understanding is the “serving size” field should just contain a number and the unit, in this case “62 g”. But for this product it contains “62 g (Valeurs nutritionnelles moyennes pour 1 portion de 62 g)”. How are applications using OpenFoodFacts data supposed to parse that? Unfortunately that information was provided by the manufacturer so it cannot be fixed…
As a non-moderator user myself, the answer is no: non-moderator users cannot change such data.
The Android app silently drops changes: you can change the data and submit the changes but reloading the product just shows the old data again.
The website shows a factory icon next to that field and has this notice at the top of the edition page:
Information identified by a factory icon has been provided by the manufacturer. It can be changed only by the manufacturer and moderators. If it is out of date or incorrect, please let us know.
So thanks for fixing the information for this product.