'… On the way back bring me 80 Security Systems. If they are short you may have to wait a while but it shouldn’t be for too long. …'
Bought precisely 80, as required.
However, reporting the mission only removed 70 of them.
Mission CompleteWelcome Back Captain. Let me do some checks…
70 units of Security System have been removed from your cargo bay.
Your Human Trade Alliance faction has increased.
You have been awarded 4,100 credits, and 410 XP.
I suspect that it was previously a mission requiring 75 units, rectified in a non-consistent way.