What kind of special TDS meter do you have that reads to two decimal points? Mine is only good down to 000, no decimal points, just a whole number. So the best reading I can get on the readout of my dual TDS meter is 000. Usually I get 001 out of the RO membrane and 000 out of the DI. My tap water TDS is somewhere above 210. So to answer your question, anything above 000 out of the DI either means it is close to being exhausted, or the TDS out of your RO membrane is abnormally high and there's something wrong there. As far as what TDS is level one should worry about, I don't know, depends on your system and what that TDS is. Salt, calcium etc. will all cause your TDS meter to register above 000, but that's good TDS. Without chemically testing your source water, or by getting a report from the city, there's no way to tell what that TDS coming out of your DI stage is. But since it's an unknown, best to sort out what the problem is.
Here's a link to your city's annual report:
http://www.calgary.ca/docgallery/bu/...report_web.pdf
Looks like your incoming TDS could be anywhere between 141 and 301. Just noticed you're running dual membranes, in which case your DI should last a long time and TDS out of the RO should be very low.