Excahgne varation parital goes to DMAAI 4340 & partial booked as COS variance

Dear All,

We observed for one case having 10 items, for some items exchange variance between Receipt price &  voucher prices goes to Exchange variance account set as per DMAAI 4340 , but for  other parts its goes to COS Variance , does system take this  to COS variance because stock was not available at the time of voucher for those item? or something need to correct in DMAAI 4340 & 4332.

Please guide.

Thanks &  Best Regard,

Mayank