Some FIR use metric flight level e.g ZUMB and 9 FIRs in China mainland. The Flight Level Allocation Scheme can be view at:
https://www.vatprc.net/rvsm
https://ais.mn/files/aip/eAIP/valid/html/eAIP/ZM-ENR-1.7-en-MN.html#ENR-1.7
When using simbrief, if any altitude is 8900m it would be converted to 29200ft. It should be converted to 29100ft according to the Flight Level Allocation Scheme. Similarly, 9200m should be converted to 30100ft instead of 30200ft.