What do starEventChance and starAutoSuccessChance mean for the Observatory?

I'm confused as to what starEventChance and starAutoSuccessChance mean for the Observatory. If they're just percentages, why wouldn't there be a percentage sign? And a 20% increase in chance grows quickly, even if there's diminishing returns (ref.). So this doesn't seem to be the right interpretation.
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Question: What do starEventChance and starAutoSuccessChance mean for the Observatory?
Best Answer
In additions to Radhil's answer, the starEventChance indicates the chance to get a star on a given day. The base chance is indeed 0.25%. Every 20 points increase the chance by 0.20%. This is because chance, the variable in the source code, is compared with a random integer between 0 and 10000. The relevant code is below (I omitted quite some stuff, but it's not necessary for your question).
var chance = 25; //25 OPTK of event per day (0.25%)
chance += this.game.bld.getEffect("starEventChance");
if (this.game.rand(10000) < chance && this.game.bld.get("library").val > 0){
var autoChance = this.game.bld.getEffect("starAutoSuccessChance"); //in %
var rand = this.game.rand(100);
if(rand <= autoChance){
dojo.hitch(this, this.observeHandler)({}, true);
}
}
So starEventChance is in hundredths of percentages, giving 0.20% bonus for each 20 points, and starAutoSuccessChance is in percentages, yielding 1 extra procent chance of automatically succeeding a celestial event for each Observatory you buy.
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