"canceling 5D with B with different timing will change the cancel's recovery period: (Timing, Recovery) (1-21F, 23F), (22-26F, 22F), (27-28F, 21F), (29F, 20F), (30F, 9F)"
Sounds like -5 is the worse case scenario as well. 5D is a lvl4 attack with 18 frame blockstun. So the further away Tao is when using 5D, the recovery time is faster if it's B-canceled on block.