Look at the spreadsheet again...

Each CRJ systems class has slots for 45 FO's. Each class will be filled first by transitions, then by new hires... they simply don't know the exact numbers of transitions vs. new hires yet. But even if the entire class is filled by transitions, they would still have to hire 45 ADDITIONAL bro FO's to replace the transitions.

My guess...expect about 30 new hires and 15 transitions for each RJ class. Unless there is significant EMB downsizing planned that we don't know about.