Then remove one of the TextInputs I gave in my example (which was to show you how to patch multiple columns)
If I'm understanding correctly, you have one list with at least two columns, one being the name of the item, and the other to hold the quantity, right? Then that list is the gallery's Item() property?
Give this a shot:
Patch(ListName, ForAll(GalleryName.AllItems,
{
ID:ID,
Column1: TextInput1.Text
}
))