If you limit your FPS to 60 you'll see that they're actually limited to 62.
The idea of this calculator is to tell you the possible values to limit your FPS so you don't get any surprises.
Also the FPS affects the game physics (movement speed, fall damage, etc.), that's why you may see players who usually prefer 333 / 250 / 125 FPS.
Notice
Although the following values may help, it doesn't mean that you should use them without thinking!
In addition to saving your current value before modifying it, it may be useful to enable the Lagometer to check for problems.
Max Packets cl_maxpackets
If you've a stable 62 FPS (and limited to that value), then you should only send 62 packets per frame. If you notice that your connection doesn't support that much, you can lower it to 32.
Personally it has been a positive change to set the Max Packets value according to the Max FPS value.
Packet Duplication cl_packetdup
Duplicates packets sent out to combat packet loss.
It's a waste of bandwidth, so use it when you've packet loss (in addition to calling your ISP to fix the problem, assuming it's not server-side).
Some players recommend using it based on ping while others until it's playable.