Two circuts on load side of GFCI?

I'm competent with GFCI and electircal wiring but I have a question about this situation. All wiring is copper with ground.
I have one hot cable coming into a receptacle and two cables leaving which each lead to a different electical outlet. Usually things are wired in series instead of this situation I have. My plan was to replace the regular outlet in this receptacle with a GFCI and just attach both of the outgoing lines to the LOAD terminal of the GFCI.
However the instructions with the GFCI say "Do NOT install the GFCI receptacle in an electrical box containing more than four wires (not including the grouding wires)." Why do they say not to install a GFCI if you have three cables in a receptacle? Is it just incase the user cannot figure out which one is hot Hot or is there another reason? Parallel wiring isn't common but i always assumed it was just to avoid confusion as to where circuits are coming/going.
Any thoughts appreciated.
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Most likely because the size of the GFCI outlet takes up more room than a standard outlet and does not leave room for another set of wires in the junction box.
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If your outlet box is large enough, you can install any number of conductors. I don't know what you're reading as I've never seen this, but just install the feed wires on the line side and pigtail the load wires together with a tail to the load side of the GFCI. Do not install four wires onto the load side of the device.

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Two points:
1. Those GFCI's occupy a lot of cubic inches and you may not be code-compliant with a lot of wires/connectors in the same box as that big fat GFCI.
2. The instructions-for-dummies that come with the GFCI help you identify common wiring schemes and do not deal with anything but the simplest cases. They're covering their ass in case someone hooks it up but leaves some downstream outlets actually upstream.
Tim.
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protected).
GFCI in a single-depth box would be overfilled. If the box is single-depth, chop it out and use a deep old-work box and you should be golden.
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Thanks to everyone who replied. This is a nice big recepticle box and there is lots of room. Everything is now hooked up and tested.
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