# their grain offering

"the grain offerings that are offered with them" or "the grain offerings that accompany them" 

# mixed with oil

"which you have mixed with oil" 

# three-tenths of an ephah

"six liters of fine flour mixed with oil" or "three-tenths of an ephah (which is about six liters)" 

# two-tenths

"four and a half liters of fine flour mixed with oil" or "two-tenths of an ephah (which is about 4.5 liters)". "Two tenths" means two parts out of ten equal parts.