Has anyone on MFP changed from Weight Watchers!!

I have change the way I am tracking my food from Smart Points to Calories. When on WW i never ate my weekly points and the program is now set to not eating any exercise points back.....so when I did do the break down i was NETTING under the 1000 calories(or close to it)......and now everyone on MFP says dont do that. I just burnt 505 calories on a walk today and MFP has me set at 1490 calarios, Do I look at my net? Or do i just go by my calories already?