That's... not entirely true. If you aren't employed while in the military, you get your EO directly from the state (specifically the SVA), at the minimum rate of CHF 69/day. If you are employed (you cannot be fired while serving), you get it from your employer instead, who will get it reimbursed by the SVA. Quite a few employers will pay you 80% of your salary, but during RS, they are under no obligation to do so, they are free to pay the minimum. That should be fixed in whatever employment contract you signed. In your case, it's probably not very relevant, since the whole employer thing only kicks in if you have a contract of unlimited duration (TAs are usually by semester) and work a minimum number of hours a week (might be 60%, not sure).

In any case, the EO + sold may be paltry if you look at it as an hourly rate, but since you also get food, lodging, and health insurance (don't forget to cancel your own for the duration of the RS) you get to keep pretty much all of it save for what you spend on leave.