Signal rate is the number of times an element changes state (high-to-low and low-to-high) per second. Xilinx tools express this as millions of transitions per seconds (Mtr/s). For example, if a signal changes at every four clocks cycle with respect to a 100 MHz (10 ns) Clock, then the Signal Rate is: 1/(4*10 ns) = 25 Mtr/s.