yeah basically if A lands at tip you add +1 to all the numbers so it would be i19 -7 +2 +4 from i18 -8 +1 +3. If its listed on the 2nd hit of the string it doesnt change the impact speed of the first hit necessarily.
This concept is labeled "impact fluctuation" and has been known since Twisted_Jester aka TharonMortis started working on frame data. Its a pity this knowledge seems to have been lost with the delete orgy over on soulcalibur.com. If some of you remember TJ used to post a list with moves of varying impact speeds right under the move speed lists in his frame data threads.
as for the RV stuff, I think it's to do with hitboxes. this stuff is much better explained on SF guides. basically mina's AA, like all moves in the game, will have a number of active frames. she will hit you up to a certain range on the 18th frame. on the 19th frame she will extend the zanbatou a little further and it can still hit you.
so if you are standing so far away such that the attack misses on the 18th frame but hits on the 19th, the blockstun/hitstun will be the same but Mina will be one more frame into her recovery, and hence recover one frame faster. hence +1 bonus on block/hit/CH
I know most players here won't be huge fans of SF but any that understand SF frames should understand this concept ok. If anyone wants I can explain more fully but might take a while