Hi,
1. You can find that in item 6, the part begins the measurement in wake-up mode, this means the ODR is around 6Hz, then 30 samples means 5 seconds.
2. Half_BW does not impact ODR, it only impact the antialiasing filter (AAF), when Half_BW = 1, the AAF = ODR/4. When Half_BW = 0, the AAF = ODR/2.
Hope these can help.
BR
Neil