OK, so I wanted to buy the Tasty Cake Collectable yeah? And I have the required number of Bells listed, but I cannot buy it, it saying I don't have enough funds. Either I made a mistake or the shop is bugged right now. Please fix. Also, if this is posted in the wrong area by mistake, forgive me.
If you had exactly 29 TBT bells when you attempted to purchase the collectible, it's because you had a fraction of a bell (i.e. 28.6 TBT) rather than exactly 29. The total amount will be rounded up to the next whole number, but the last bell isn't actually available to be spent because it's not a whole bell, if that makes sense. It looks like you have more than enough now after making a few posts, so give it another try and let me know if you're still having issues.