It's a bug in blockchain.com's algorithm...
blockchain.com is just a block explorer... They just run a couple of nodes and parse the blocks and unconfirmed transactions they receive. If somebody messed up the parsing code, you end up with things like negative balances. This bug has no significance in the real world, blockchain.com is not the owner of bitcoin, it's just a private company that builds things like an online wallet and a block explorer.
Most other blockexplorers are probably fine:
https://blockchair.com/bitcoin/address/1Fr8qEa7vcwJikeW9q6thaYZPacGY5CQAb
