… is measured in samples. Not bytes or mils.
So if you want to know how it relates to the ByteArray you’re working with, you need to multiply it by 4 (as each floating point sample requires 4 bytes). And if you want to convert it to mils, you need to divide by 44.1, the number of samples per millisecond.
I expect you’re wondering why I’m discovering all this stuff. Watch this space 🙂