I am reading "Java Concurrency In Practice" and am stuck at one calculation presented in Amdahl's law section. Full text is also available here: https://flylib.com/books/en/2.558.1/amdahls_law.html
" With ten processors, a program with 10% serialization can achieve at most a speedup of 5.3 (at 53% utilization), and with 100 processors it can achieve at most a speedup of 9.2 (at 9% utilization). It takes a lot of inefficiently utilized CPUs to never get to that factor of ten."
I understand the speedup calculation but how is the CPU utilization came to be 53% in first case and 9% in 2nd case?