Discrepancy between old chain length and largest chainring largest cog method
If you are counting links it’s easy to mess up, but it is possible your chain was too long if your rear derailleur had extra capacity to deal with the slack (but not 7 links I think). 

Determine chain length using the method in the video below, mark the rivet where you would cut. If you do this properly, making triple sure the chain is on the biggest ring and sprocket, you will not end up with a chain that is too short.

Lay the chains next to each other to compare lengths instead of counting links or rivets.