瑜伽論記 8.43

8.43

義曰：四作意是七作意外故名餘，此四作意是四十作意中作意，今收入七作意中六故，故言攝入六作意中。

The meaning is: The four attentions are outside the seven attentions, hence called 'the remaining'. These four attentions are attentions among the forty attentions; now they are subsumed into six among the seven attentions, hence it is said 'subsumed into the six attentions'.