I replaced the floor with a ceil operation to ensure that we always show at least “1 minute”.
Also, it will try to choose the maximum between the old formula (word count / read_time_word_count) and the minimum reading time (4 seconds per post; 4 because that is how long it takes me to read a short post or see an image and scroll to the next post). 
For that topic, the formula gives 6 minutes. I managed to read the topic in a little under 6 minutes, so I’d say it works fine. 