The People’s Bank of China (PBOC) set the USD/CNY reference rate at 6.3674 on Thursday while comparing to the previous fix and the previous close at 6.3735 and 6.3680 respectively.
"With 10 billion yuan worth of reverse repos maturing on Thursday, China central bank injects 90 biillion yuan on a net basis on the day," said Reuters after the PBOC fix release.
It's worth noting that market expectations backed 6.3669 as a quote before today's fix published. The reason could be linked to the downbeat US dollar and firmer yields.