If you follow the NFL draft value chart, the #11 pick is worth 1250 points.
The Broncos had #15, which is worth 1050 points.
So the Broncos had to make up at least 200 points to make the trade.
They had a 3rd round pick, 68th overall, worth 250 points.
So I think the Rams got the 68th pick out of this.