[argyl53]

Well, you’re sort of right. Computers can only generate pseudo-random numbers based on an input “seed number” to an algorithm, however gambling software utilise either hardware or software generated cryptographically secure pseudo random number generators. In short, either RNG hardware which measures unpredictable quantum phenomena such as a photon passing through a partially reflective surface, or software measuring equally unpredictable device phenomena such as open file handles, processing threads and the like, are used to generate the input seed which makes the resulting number sufficiently random i.e. not based on microtime and therefore not even in principle predictable in advance.