This swap wasn’t successful; it failed. Even a failed transaction on Ethereum costs gas. The error given, ERR_LIMIT_OUT, implies that the price slippage was beyond your tolerance, so the transaction reverted to save you from front-running. When the price moves very fast, transactions can occasionally fail. The default slippage tolerance is 0.5% and it can be changed within the Balancer Exchange (there is a gear icon at the top-right of the modal). If you suspect that the token pair you are trading might be volatile, it’s best to increase the slippage tolerance to 1% or 2%.
The reason for this is that if you accepted infinite slippage, for example, someone could spot your transaction in the mempool and make a “sandwich attack” on you. This user would buy a ton of xHDX, then let your transaction go through (so you’ve now bought at a much more expensive price than you were quoted on the UI), and then the user would sell xHDX at the markup created by your purchase to turn a quick profit. So slippage tolerance is very important, and there’s a reason we have it set at 0.5% by default: it’s high enough to let most transactions succeed while still low enough to protect from the occasional front-run attempt. Of course, every once in a while, in a volatile market, a transaction will fail. That stinks but it’s the best-case scenario.