Complex sentence: Since 25 August 2017, Bangladesh has received at least 480,000 refugees, adding to the 500,000 refugees who arrived during earlier crackdowns, including 66,000 who arrived since October 2016.
Split into simpler sentences: Since 25 August 2017, Bangladesh has received at least 480,000 refugees. This added to the 500,000 refugees from earlier crackdowns, including 66,000 who arrived after October 2016.