These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.99 s (backtrack: 0/20).

[ebuild  N     ] acct-group/vnstat-0-r1::gentoo  0 KiB
[ebuild  N     ] acct-user/vnstat-0-r1::gentoo  0 KiB
[ebuild  N     ] net-analyzer/vnstat-2.13-r3::gentoo  USE="-gd (-selinux) -test -verify-sig" 329 KiB

Total: 3 packages (3 new), Size of downloads: 329 KiB