Corrected entry: To sneak Orac into the Casino, Avon tricks it into reducing its own size by claiming that it is impossible to do so, whereupon Orac immediately shrinks itself to prove otherwise. Knowing in theory that it is possible is one thing, actually doing it immediately without the use of any other equipment is just plain silly. What practical device or physics did Orac use to perform this miracle? There are only two possibilities for shrinking an object to, for example, 1/4 of its size. (1) You can remove 3/4 of the atoms in it. Orac might still be functional doing this but would never be able to be upsized to original size again (since 3/4 of the molecular content is now lost, you'd end up with a "pixelized" version of Orac on re-expansion). (2) You could compress the available atoms into 1/4 of the physical space, which would made it 4 times as dense, and therefore as stable as a nuclear bomb, with a gravitational pull similar to that of a neutron star. Apart from the fact that physics are different for objects of that density and so electricity, for example, wouldn't work anymore: if Orac used this method, its voice would have changed beyond the range of human hearing.
Corrected entry: Avon and Vila seem obsessed with a pointless exercise. Initially they plan to break the casino by winning a million credits with Orac's help, but Vila can't stop and gets their winnings up to 5 million, then risks death by electrocution by playing the Klute at Speed Chess for more. But when the Liberator was first boarded in Series 1, the crew found a room containing riches beyond imagination - currency, gems, etc. There are at least 30 million credits worth in there, because that is how much Jenna offered the hijacker of the Liberator in 1.11 'Bounty' to let her go.
Correction: The point is that they are bored, not that they need money.
Correction: This is simply untrue. Orac is light enough to be carried by hand. Compressing him to much smaller size would quadruple his density, making him about as dense as an iron weight. It would certainly not increase his density to that of a neutron star (which wouldn't increase his gravity anyway) or to nuclear densities, both of which are many many powers of ten larger than what is seen here.