That's not a good description of mayday - mayday is cumulative damage, just like Book 2.
Bottom of page 8, top 'o page 9 describes the results of hits:
Weaponry - ALL weaponry is disabled.
Computer - the computer has been rendered non-functional.
M-drive - the maneuver drive is disabled.
J-drive - disabled.
And, any ship which receives 4 or more hits in a single turn is destroyed.
It more resembles the crit table in Book 2 and HG than the incremental damage from typical Book 2 hits.