Repro:
1. Go to https://omahaproxy.appspot.com/
2. Put 50.0.2661.89 in "Version Information" box and hit Lookup
3. Look at "Branch Base Position" in results.

What is the expected result?
"378081"

What happens instead of that?
"619"

You can see the incorrect result in the deps.json response:

  https://omahaproxy.appspot.com/deps.json?version=50.0.2661.89
  =>
  {..., "chromium_base_position": "619", ...}

For versions that appear in the CSV Viewer table I would expect this line to match the "branch_base_position" column, which shows the correct value.