My weight goes up and down!

Hi, im kinda new here. I started the calorie count last August 20. So today is my 20th day. So far I have lost a total of 10 lbs.

I would like to ask why does my weight go up and down?There was a time wherein I gained 2 lbs but the trend says my weight is going down. Actually my actual weight became equal to the trend (amazing).

I try MY BEST to maintain the calorie intake to about 1400 but i usually end up around and average of 1600 calories a day. I weighed in when I woke up (which is what I usually do) I am 170 lbs already from 180 lbs. BUT the trend says that I am 172.64 lbs, why is that?

Hope somebody here can shed some light on this. Thanks