No, the 78x1x-serial consists of two secretly connected numbers (to say so) ... the xx usually denotes the individual aircraft within a regiment, while 781 denotes the Brigade by 781 - 611 = 170. Brigade.
This pattern however works only for the Brigades, for the regular Divisions - as with the second serial - You have to use a different one: 1Yx3x - 11 = 2. Division. Here the Yxx-number is a bit different to the xx used by the Brigades:
the first regiment within a Division has numbers from Yxx = 001 to 049
the second regiment within a Division has numbers from Yxx = 051 to 099
the first regiment within a Division has numbers from Yxx = 101 to 149 or 150
That's the mystery of the PLAAF's serial system and that's the reason why I'm so much interested in the full serials ....
Deino