Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: I own 3 of these & noticed odd thing. When removed from refrig, circles appear on top cow cover in glass.Anyone else notice ?
Document: Received on 23 April 2012. First thing I noticed was a 1 inch curved crack in the larger piece. Thought it was shipping damage. But the crack didn't reach the edge of the glass. It in the side of the piece.Then I noticed a depression in the glass near the crack. The depression was about half an inch across and the glass was about half the thickness of the surrounding glass.The factory shipped a defective glass butter dish to the US.
This is the best butter dish! I bought 2 so that I'll always have a clean one available. The cow on the cover is so cute. I put 2 sticks in at a time and my butter knife fits in between them. I'm planning to buy more and give them away at Christmas.......but don't tell anyone! If you need a new butter dish you can't miss with this one!
My house has gone without a butter dish for years. It drives me absolutely bonkers that the cover of a typical butter dish smooshes the top of the butter. This is a nice large vessel that could easily hold two sticks of butter if needed. And I love the adorable foraging cow on the cover.
My wife wanted a butter dish to handle the wider butter sticks like Plugra (not imported, made in the USA, rated #1 by a couple of evaluators) and to look good doing it. This product is substantial heavy glass that can be used as a tub to hold the butter or reversed to provide a flat surface with domed cover. Not slippery to drive hands. From what we can tell, it's the real thing, not a knock off.
I hate the butter dishes that have the covers on top because if by chance any butter melts it makes a huge mess on the counter. This butter dish is aces at not letting that happen. You can fit 2-4 sticks of butter in the dish and the nice cover keeps it safe from cats who jump on the counter and lick the butter. I like the design on the cover and this dish is good solid glass, not cheap and it won't break if it gets knocked around by clumsy teens.
This butter dish is perfect for my farm table. The cover is easy to handle without being too hard to grasp. The only thing I&#34;d like better is one that holds just one stick of butter.
Love the cow on the cover and is glass. Keeps butter well and can actually fit two sticks in there.
This is a cute glass butter dish and was exactly what I was looking for. Butter goes in the larger part and the lid with the cow goes on top. Not messy at all and keeps a cube of butter nicely. I'm ready to order a second dish for when one is in the dishwasher. Highly recommend this product.
I adore this butter dish. I have a country home and don't like tacky country style. This is subtle coutry being glass with the cow on top and tasteful. Its perfect for the butter I make or the blocks from the store. I am thinking I may need to order some of these as gifts for my friends.
I'm very happy with this purchase. Like some other reviewers, I use it upside-down, with the cow part on the counter and the large dome part on top. That way I can cut butter slices off the bottom dish without smearing it all over the inside of the dish. The dish is large enough that a regular stick of butter has ample room around it, so it's not going to smush into the domed glass lid, even if you don't line up the butter perfectly in the center.
Answer: I'm putting mine in the fridge now to see if that is always the case....but, if  I had to guess...it would be inherent in the process of making the glass lid from the molding process. Perhaps caused by suction cups removing it from the mold while still warm, hence forming a barely noticeable impression only obtained when coming from the cold refrigerator to room temp. I also noticed this abrogation when cleaning the window panes of our house. When wiping them clean after washing, you can detect perfect circles that seem to be embedded in the glass. Those marks are from the suction cups used in handling the glass during manufacture, hence I deduce it to be the same phenomenon you are seeing with the butter dish lid. Of course this is all deduction and may not suffice in reckoning the reality of said observance.