What that action is doing is taking segment 1 from your spoken command and converting it to a decimal and placing it in the decimal variable named, 'XPLANE!SIM/CUSTOM/XAP/TR_CODE_1'.
The variable 'XPLANE!SIM/CUSTOM/XAP/TR_CODE_1' is from a profile that was created by someone else.
So, for instance, lets say you had a spoken command like 'Turn[90;180;270]degrees'
and you said, 'Turn 180 degrees' to execute the command.
{CMDSEGMENT:0} within the executed command would render as 'turn', {CMDSEGMENT:1} would render as, '180' and {CMDSEGMENT:2} would render as, 'degrees'. What the action would do in this case is convert that, '180' into a decimal and put it into the decimal variable of 'XPLANE!SIM/CUSTOM/XAP/TR_CODE_1' so that its value can be used later (possibly within a plugin).
Hoping that makes sense