Transactions on 8949 Disappeared

I ran the 2017 report for an amended return and had about 112 pages of transactions on the 8949 form. I recently received about 1500 more transactions from my history on Bittrex so I imported it and ran the 8949 report and only have about 15 pages. Shouldn’t there be more and not way less with adding transactions from another exchange?

Actually it looks like they are aggregating transactions for the same coins and combining them on the 8949. I didn’t realize that was acceptable to the IRS. Is it?