Is contacting police federal mandate ?

Anybody here who can advice ?

Your visa should state duration but visas I've seen in the past were at least 90 days from first entry, extendable at PF previously in Pca Maua, more recently at Galeao Aeroporto Int.
It should be on the visa stamped in your passport.
Personally never had type you're speaking of.
Fyi, if you ever need to go to that division of PF GO EARLY! Last I checked same locale used for Brasilian passports so don't panic if 30 - 40 already waiting to open.
May be by appt only as its been a couple yrs since I went.
Also check holidays and any reason they may have for not being there and really helps to have everything you'll need in hand.
Fyi, much improved, and generally good people working that sector, since my first encounter. (In '75) :^)

My visa duration is 90 days however at the bottom line of the visa there is statement " please contact federal police within 30 days " , not sure what it is ..

Almost certain that means within 30 days of your 90 days expiration.
Probably in case you want extension.
Many in past wait til 88-89th day and didn't have necessary docs, photos, etc...
You don't have an issue until 60+ and still could legally stay until 90th.
Keep in mind you probably flew overnight so arrival day in Brasil is first.
Fyi, usually 180 days from first arrival per yr, not final 180 of 16 & leave, return beginning of 2017 for another 180.
Meaning you can not fly to Argentina for a night and start the clock again and they will often sit there and count days in n out.
Also don't try to enter with only a week on visa or on days/ year.
Long boring day sitting at airport until boarding same aircraft you arrived on.
They are not flexible just like the USA not with them. All reciprocal.
Enjoy

Hello my kind friend

I feel in my experience you do not need to worry as long as you leave within the duration of your visa....
I think you only need to register with the federal police if you are going to be living/working in brazil