decrease it if you haven't got a powerful CPU, Very low should be ok for 2-4 cores Amd Cpus and 2 cores Intel Cpus (2 Threads), low and normal for 2-4 cores Intel Cpus (4 Threads) and 6 cores Amd Cpus, high for 8 cores Amd Cpus and 4 cores Intel Cpus (4-8 Threads) and very high for 4+ cores Intel Cpus (8+ Threads).