The total precision represents the total bytes needed to move the largest row of data. For example, if the total precision equals 33,000, then the Integration Service requires 33,000 bytes in the buffer block to move that row. If the buffer block size is only 64,000 bytes, the Integration Service cannot move more than one row at a time.
As with DTM buffer memory allocation, increasing buffer block size should improve performance. If you do not see an increase, buffer block size is not a factor in session performance.