It seems your 'Update query rows' function isn't updating the queried row. The last value, according to your logic, should be 50, but it's still 70. At least, that's on the latest Construct 2 build. Can you please investigate?
I do the following events in my own project, trying to update a key value of one row that is identical to another row in a different DB:
Filter- 1. Create a new row filter
Filter- 2. key "A" value is equal to [DB2 'Index2QueriedRowContent', key "A" value]
Filter- 2. key "B" value is equal to 1
Update value "B" to 0 in all queried rows
...and value B in the DB does not update. In fact, there doesn't seem to be any value that I can update in my first DB, using the identical data from a different DB to filter for it.