It seems that Counter damage for the automaton might be 50% of normal hits (or at least the average anyway).
This was done during Overdrive and with Galvanizer and 1x Thunder Maneuver (same conditions as for the previous post)
Code:
Critical hit (n = 35)
Min 538
Max 664
Average 615.5714286
Hit (n = 59)
Min 392
Max 516
Average 459.779661
Non-counters (n = 94)
Sum 48672
Count 94
Average 517.787234
Counter (n = 43)
Min 159
Max 421
Average 254.8444444
43 counters out of 102 counter opportunities (misses and parries excluded) as well (results consistent with the documented 50% counter rate for Galvanizer with 3x Thunder Maneuvers)