He was held for four years before being found guilty, with that first verdict giving him 15 years. Not sure what to make of the 2016 part, I think that refers to the date of his first trial.
Here's what the NY Times has on it:
"Last month, a court ordered Mr. Schellenberg to be retried after he appealed a 15-year prison sentence for smuggling methamphetamines. ... After his arrest [in 2014], Mr. Schellenberg was held for 15 months before his first trial, and it took an additional 32 months before a court declared him guilty and sentenced him to 15 years in prison for his role in a failed attempt to smuggle drugs from China to Australia."
https://www.nytimes.com/2019/01/14/world/asia/china-canada-s...