Honestly I guess these credits are given by bots, rather than actual people. I had a maximum of 75 and other two got 32 which is weird because a human wouldn't judge a post on the same parameters. Bots aren't affected by the words written in a trip but humans are. And getting same number of points every time is pretty much an evidence of calculated behavior which is unlikely for a human.
I published 3 trips so far and received 70 for two and 50 for one. which clarifies that 70 for trip is not fixed. It varies and according to my guess, it varies based on the traction you receive on your trip/blog.