What are thresholds in SQL Server 2014 "big table join to small table" cardinality estimation optimization?
The whitepaper does not define "large" for any examples, it uses the terms "large" and "small" to help explain the math the new CE is doing compared to the legacy CE. 

The section you referenced shows a join predicate that contains a mix of equality and inequality predicates. The new CE will look at the rowcounts for the tables and determine which one is "large", and use that for the estimate. The legacy CE didn't look at rowcounts, it would just multiply the selectivity of each predicate. 

HTH