Questions about the commit_fee calculation

[ShookLyngs]

Assume A has a channel A/B, and B has a channel B/C:

1. A opens an A/B channel and pushes 1000 sat to B.
2. C generates a hold invoice of 1000 sat and asks A to pay for it.
3. A pays the invoice through the A/B channel, where a pending HTLC of 1011 sat is added to the channel.
4. Before C settles the invoice, A decides to close the A/B channel, leaving a pending HTLC in the closing transaction.
5. The closing transaction paid a miner fee of 328 sat.

My questions:

1. Why did A pay 1011 sat to B in the A/B channel? Was the 11 sat a fee to B?
2. Why did the closing transaction pay 328 sat as the miner fee?
   1. This is an ANCHORS commitment type channel, so the estimated commit weight should be 1124 + 172 * num-untrimmed-htlc-outputs, where num-untrimmed-htlc-outputs = 1, making the weight 1296.
   2. Calculating the fee with the estimated weight, where the fee_per_kw for the channel is 253 at the moment, the fee should be: 1296 * 253 / 1000 = 327.888. The result should be rounded down, so Math.floor(327.888) = 327.
   3. So the fee should be 327. Why was it 328 instead?