In insturments section:
Vol env Hold(s) : Indicates how long the note will be held before entering the Decay position. //This setting can be "~ 0.200" for instruments such as Piano and Guitar.
Vol env Decay(s): Sets in how long the note should reach the value in the "Vol Env Sustain" setting from the current setting. //This setting can be "~19.0" for instruments such as Piano and Guitar.
Vol env sustain (dB) : A value of 144 is for full fade out. Given a value of 0, the above settings has no effect.
This is an instrument specific description.
Note: For "Vol env Decay" and "Vol env Release": Although the values are given in seconds, due to some definitions in the soundfont specification, the time you will give may sometimes need to be (2x to 6x) longer than the result you want to get. So adjust it by trying and listening.
Normally, the person using the soundfont does'nt know when the sample entered the loop state. It can happen after 1 second or after 11 seconds.
But if there is a special case, you can look at the samples one by one and arrange the "Vol env Hold" setting accordingly.
How to find (You don't need to use this unless you have a very specific reason):
Hover over the sample's graph with the mouse. Keeping the right button pressed, drag the mouse to the right (zoom), placing it over the loop-start line.
Then hold down the left mouse button on a blank space to the right of the Loop start line and adjust the graph until the loop-start line is at the far left of the window. You can now read the loop-start seconds at the bottom left of the graph.
Thank you for the answer. My goal is to produce smaller sized sounfonts for phone or tablet. For this reason I don't want to use long sustain samples. I need very short and looped sustain samples and yes for guitar. The user sf2 examples on the site are too bulky and large.