If the value of this parameter is set to a modest value, the MS may retransmits the RLC data block before the BSC sends an Uplink Acknowledgment message. Thus, many radio resources are not used but occupied.
If this parameter is set to an excessive value, the speed of the sliding window decreases and the probability of the uplink TBF transmission countdown increases, thus decreasing the performance of uplink transmission.
To make this value more accurate, you need to estimate the delay in the transmission between the MS and the BSC first. This value is set based on the transmission delay.