I was able to buy something slightly over my unit amount []

I was buying items at D.I.Y., it was a large set of items because I wanted at least 10 of everything, so it was ~60 items. I set a list of items I wanted to buy, noticed the price was too much and had to decrease it. To my recollection, I had ~33,000 units, and the price was ~34,000 units, 1,000 units over what I had. However, the “purchase” button wasn’t greyed out, and it let me purchase them, even leaving me at 4 units. However, when I left the lobby and entered my condo, I was at 0 units.

Unfortunately, I didn’t get any pictures of it, as I didn’t think about taking pictures until afterwards. I do, however, have a picture of me with 4 units.
And a picture of me with 0.

Update: Redeeming a treasure chest (+5000 units) brought me up to 4,574 units. (I redeemed another afterwards, thus why I’m at 9,574)