TFS branch mapped to multiple workspaces, where will pending change go when branch choosed as merge target?

I have two Branch: DEV and Future;

for DEV branch, it is used in two Workspaces on my local machine, WS1 and WS2;

in WS1, DEV branch is mapped to C:\DEV, in WS2, DEV is mapped to E:\DEV;

Future is mapped to C:\future in WS1 and not mapped in WS2;

I open solution from E:\DEV, and in source control explorer, choose to merge from Future to DEV. The result is pending change is shown in WS1.

Since DEV branch is mapped to both WS1 and WS2, why the merge pending change only shown in WS1, how can i make it to show in WS2?