There may be an error in a lecture video: Chapter 6

In this lecture video:

Chapter 6: Aggregation Performance and Pipeline Optimization
Aggregation Pipeline on a Sharded Cluster

At time 3:06 the video displays something like:

db.movies.aggregate([
{$limit:10},
{$limit:5}
])

once optimized becoming:

db.movies.aggregate([
{$limit:15}
])

But things don’t seem to work that way, as we should expect (the result is 5 and not 15):

…PRIMARY> db.movies.aggregate([{$limit:10},{$limit:5}]).itcount()
5
…PRIMARY>