The answer is the parameter that's being passed in. That's used to seed the random number generator.
Random rand = new Random(seed);
PRNGs are not truly random - they are deterministic, but are designed to simulate randomness. For this reason they are better termed "pseudo-random number generators".
For a given seed, a PRNG will always generate the same number. It then likely uses its last result as an input to the next value, so by seeding the PRNG with a known value, you will always produce a known sequence of "random" numbers.
The numbers -229985452 and -147909649 are known to be seeds which will cause that particular PRNG to produce a sequence of 5 numbers that can be interpreted as "hello" and "world". If you were to change those numbers, you would get different 5-character sequences, but they would be the same for every run of the program, so long as the seed remains the same.
