That is what I would expect. Those are reasonable times.
With the information given it’s hard to say. Log out the 1000*i to make sure there isn’t something odd going on there causing the Timer to be scheduled longer into the future than expected or something.
Add logging inside the timers to see when the timers are triggering. There are only two threads for running timers. So if you have a bunch of timers or cron triggered Rules then these timers may have to wait on other timers to finish running first before it can run.
If you have more than one Rule that controls the Items in this Group, consider the Design Pattern: Gate Keeper Queue example. There might be an interaction between the rules that send these commands that isn’t apparent.