Overriding attribute LOC

Hey

I get this error after wrinting my lpf constraint file, i made sure that 
i assigned the correct pins , i don't know why i am getting this error:

In "LOCATE COMP "d0_ch1_p_i" SITE "F9" ;": Overriding attribute LOC with 
F9 from preference file

i am working on LIFMD6000 device and i am compiling my code in 
lattice-diamond.
Could someone tell me what could be the cause.

thanks