Edit2: network difficulty is calculated based on the frequency of the submitted blocks at the given difficulty, so it is very random for Spots within several blocks time frame.
regardless, the math on this server is incorrect and that's why it took over 1 hour to mine one block. hint hint, the difficulty does not match the hash rate. hint hint 2, the formula that calculates the difficulty is broken
What server are you talking about? Are you talking about Spot client or are you talking about some pool?
Difficulty adjusts only based on the time it took to mine last 2 blocks and not based on anything else.