Map tab grouping different tiers of the same map when listing for sale in bulk

So basically if I have say T13 Arid lake listed at 5 chaos for 2 maps, but have only 1 tier 13 map, however I also have 1 T16 Arid Lake map the trade website will show that I have 2 for someone looking at listing for T13 Arid Lake that I have priced and whisper me for them.

I hope I explained this well.