Extra byte in advertising data?

The manufacturer data from a peripheral seems to be getting an extra byte...

My peripheral is sending these bytes:

0x0c 0xff 0xe5 0x02 0x00 0x01 0x01 0x00 0x00 0x00 0x00 0x00 0x00

• The 0c means there are 12 more bytes coming.
• The ff means it's a manufacturer message.
• The next 2 bytes are the manufacturer id.
• The next 9 bytes are the custom manufacturer data.

Here's what I'm getting from CBCentralManager.didDiscoverPeripheral:

  advertisementData: {
      kCBAdvDataIsConnectable = 1;
      kCBAdvDataLocalName = "SQ-SPT-0021 432190009";
      kCBAdvDataManufacturerData = {length = 12, bytes = 0xe50200000101000000000000};
      kCBAdvDataRxPrimaryPHY = 0;
      kCBAdvDataRxSecondaryPHY = 0;
      kCBAdvDataServiceUUIDs =     (
          "00000100-34ED-12EF-63F4-317792041D17"
      );
      kCBAdvDataTimestamp = "681852653.472335";
  }

... here's what I would expect in the 'kCBAdvDataManufacturerData' vs. what I'm getting:

     0x00 0x01 0x01 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x01 0x01 0x00 0x00 0x00 0x00 0x00 0x00

I lined these up to hopefully show that there's an extra 0x00 byte at the beginning (this is clearer with more non-zero bytes, but I didn't want to make up data, and I don't have the old data available).

Where is this extra byte coming from, and how can I get rid of it? Changing the peripheral data is a possibility here.