it said my pc is in the recommend requirements so why the fps is low? help pls

my pc:
Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
cpu speed:3.6 GHz
ram:4.1 GB
os:Microsoft Windows 7 Professional Edition Service Pack 1 (build 7601), 64-bit
video card:ATI Radeon HD 5400 Series
sound card: ATI HDMI Audio
free disk space:1.2 TB