Re: Need to understand music concert Tech Rider.

What you are reading is "tech short hand"
Let me answer your original question,
1. SH604 > This would perhaps be a Euphonics SH604 noise gate in rack frame 1.
2. Most mixing desks have grouping either 4,8,16. these allow sections of the mix to be "grouped" together and then controlled as a single block rather than individual mics, and the two numbers refers to which group and how the panning may be assigned.

In audio many / most items are referred to as model numbers rather than by maker.
At times the language that audio people use may seem quite foreign but most occupations have their own abbreviated terminology.

The difference between Knowledge and Wisdom is... Knowledge is the knowing of facts.... Wisdom is the sensible application of good quality knowledge...