Explanation for the Lowpass filter

Hello,
I have a signal as shown here **broken link removed**
and I want to design a lowpass filter in matlab.But for this I need to select the frequency part parameters like Fpass,Fstop,Fs and for magnitude need to slect the Apss and Astop.
From the signal above shown I am clear with selction of Fs should be >10Hz.But I am confused with Apass,Astop,Fstop,Fpass.
Can someone how they need to be selected to get a cutoff freq of 3Hz I mean how the value(increase or decrease) effect on the filter design and on the output(filtered) signal.
I tried designing a lowpass as shown but I wondering what are these in the red marked region of image.
The actual LP filter should look like this https://upload.wikimedia.org/wikipedia/commons/6/60/Butterworth_response.svg what is the difference of one desinged and one in wiki in both.
Can anyone expalin about this.
Thanks.

The lowpass as referenced by you (wikimedia) is of FIRST order with a slope of -20 dB/dec.
The question you have to answer is: Does such a simple lowpass fulfill your attenuation requirements?
A lowpass has the task to let path the desired signal and to attenuate unwanted frequency components - and that is the meaning of the parameters Fpass,Fstop,Fs, Apss and Astop.
(Frequencies F and the associated minimum damping requirements).