Why do our thirteen FR10 fixture kits contain only ten locating blocks?

Stores opened the sealed accessory box and counted ten locating blocks for thirteen FR10 fixture kits. We have the other listed contents. The seller says the quantity means individual pieces, although their final message specifies one block in each kit. I have marked three kits incomplete. What is the clearest way to get the missing-block balance acknowledged without arguing about the total number of unrelated pieces in the box?