Jenn1972, welcome to the community. I am sorry about the substitution. I don't think that you will get credit for the substitute potatoes. Most offers are specific about the size. Double check the offer details. If it says the 8 oz only, you won't be counted. Again, I am sorry you have to deal with this and welcome to the community.
@Jenn1972 Yes, you have until it expires from your gallery. Look at your list for Walmart, then click on that item to open it up. It should tell you an expiration date. Some items don't have a date of expiration.
I still need to get the Great Value onions. I see I have 'til next week to get it.