There are too fucking many nuances to describe in a forum post but I’ll try to hit the high notes.
a) In theory almost everyone is eligible to be drafted. Males 18-60 except those too disabled to work and some women with the right education.
b) Formally speaking mobilization is supposed to be declared in “waves” and the current one only supposed to be aimed at recruits of “first wave” (youngest and the best-prepared), and even then no more than 300k of them. In reality it seems they did draft some of the 35 years+ guys already, so nobody really knows wtf is going on.
c) To get drafted you must be served a “summons” - it is the same word that is used for the court summons except military commissars are empowered to issue them on their own. Like with the court summons they have to either have your signature or a signature of two witnesses that it was delivered to you (importantly - to you personally, dropping it at a place where you live is not enough)and you refused to sign. I haven’t heard about authorities fabricating a signature yet.
*there were recent changes that 18-year old guys are supposed to deliver themselves to be conscripted without summons, but that’s only for them the rest are still running on the “summons”
d) Even if Russian authorities wanted to draft everybody they literally have no state capacity to do so, normally the system relies on making an example out of few troublemakers and it is enough to keep it running smoothly (just like many other aspects of a human society - taxes, driving, etc). What would happen now is anybody’s guess, my personal guess there would be enough people complying with the soft power to throw more meat into the meatgrinder but most people who want to evade being drafted and willing to sacrifice some aspects of their lives for that will be able to do so.
e) Worst case scenario there’s still an alternative of going to the prison. Prisons here are probably among the worst in Europe (maybe some Balkan countries or Turkey could be a contender) but unless something out of usual is arranged for “draft dodgers” it still may be a reasonable choice, at least if you don’t expect to have to serve the whole 10 years (which is likely, recent law threatened 15 years for “spreading disinformation” about Russian Armed Forces but so far all the prosecutions resulted in heavy fines and not a single prison sentence).
All in all - Russian authorities do not seem to want to drag everybody to the front, and wouldn’t be able to if they wanted. System seems to be running fine on the usual threats of consequences instead of having to drag each conscript kicking and screaming.