I don't use Shayan's but it's possible that the subrace uses the inherent bonuses for its base race to get the +6 dex, for example. If Gith use elf as a base race, elves naturally get +2 dex, -2 con. So, a Gith would need +4 dex additionally to get a +6 total. Not sure if this is how it is intended to be read. If Gith don't have any CON penalty, (as elves do), then the subrace script would also have to add +2 to the CON (plus the intelligence and wisdom bonuses).
Another possibility is that what is stated in the description is not what is implemented in the code.
Do a search in your module for the "effectabilityincrease" command.
1) Open the module in the Toolset
2) Open a script (any script)
3) Click on the 'Find In Files' icon on the top row of icons (it looks like a magnifying glass in front of a tan file folder - it it NOT the 'find in text' icon right next to it)
4) Type "effectabilityincrease" in the 'Find What' field
5) Click the "Find In All Files in the Module" radio button. This will make the search go beyond just the file you have open
6) Click 'OK'
In the bottom third of the screen, a list will appear of all the scripts and each line within those scripts that use that command. By clicking on each one, it will either open up the script or take you to the line within it.
From there, you can scroll around to find where the Gith subrace is handled and look at what ability changes are given. They're probably all together. Each subrace is probably given ability changes in the same file, so by scrolling up and down in that file, you can see, as far a abilities go, how they differ.
What's more, you can change the subrace abilities by altering the code.
You'll see a command such as this:
EffectAbilityIncrease(ABILITY_STRENGTH, 1);
This gives the recipient +1 strength. Change that to any number between 1-10 and it will change the system.
Also, you can repeat the above for "EffectAbilityDecrease", which is used to apply penalties to abilities, though you'll probably see it as you look at the increases.
Lastly, once you save the changes and exit the script screen, you'll likely need to BUILD your module (i.e. have the engine recompile all the scripts) before you save it. Otherwise, your changes likely won't take effect. This is as simple as hitting the Build option on the top row of your module (File, Edit, View, Environment, Build...). Select Build Module. Wait a few minutes. Then, Save As your module to a new filename (don't save it over your original module).
Play your module and enjoy your modifications.