This is a read-only value reporting the maximum number of frame-blocks allowed in an interleaving group for this active AMR-NB call, where frame-block level interleaving spreads consecutive frames across time to improve resilience to burst packet loss, applicable only when the call uses octet-aligned framing with the AMR-NB coder. An admin checks this to confirm whether and how aggressively interleaving is being used on a live call, which trades added playout delay for better loss resilience. For example, a network with frequent short bursts of packet loss might benefit from interleaving, and an admin would check this object to confirm it's actually configured and active on affected calls.