// At the top of your file
new
    gTimerMinutes = 1,
    gTimerHandle;


// In Script_OnGameModeInit:

INI_ParseFile("settings.txt", "settings_%s");
gTimerHandle = CreateTimer("function", gTimerMinutes * 60000, 1);


// Elsewhere (not in  function):

forward settings_timer(identifier[], text[]);
public settings_timer(identifier[], text[])
{
    if (!strcmp(identifier, "minutes"))
    {
        gTimerMinutes = strval(text);
    }
}


// In settings.txt

[timer] ; tag same as in settings_timer
minutes = 2 ; identifier of minutes, 2 is actually a string, hence strval