• The for loop runs some_script.sh 10 times, measuring its execution time with time
• The stderr of the for loop is redirected to stdout, this is to capture the output of time so we can grep it
• grep ^real is to get only the lines starting with "real" in the output of time
• sed is to delete the beginning of the line up to minutes part (in the output of time)
• For each line, awk adds to the sum, so that in the end it can output the average, which is the total sum, divided by the number of input records (= NR)

The snippet assumes that the running time of some_script.sh is less than 1 minute, otherwise it won't work at all. Depending on your system, the time builtin might work differently. Another alternative is to use the time command /usr/bin/time instead of the bash builtin.