Interesting.
Eric is right in that PlannedVelocity is the column you're looking for.
The two values that go into the equation are PlanEstimate and PlannedVelocity.
Both are available through WSAPI, but interestingly the Excel Plugin does not let you query for PlanEstimate, even if you add it manually to the wanted columns (usually this works).
I am guessing that PlanEstimate is not available in WSAPI 1.43, which is the API version the Excel Plugin queries on.
Note that the cooresponding WSAPI 2.0 call would look something like :
https://rally1.rallydev.com/slm/webservice/v2.0/iteration?query=(Project.Name%20=%20%22Jump%22)&fetch=PlannedVelocity,Pl…
Whose first result matches the attachment below :
{
},
PlannedVelocity | PlanEstimate | Project |
13 | | Jump |
23 | | Jump |
30 | | Jump |
15 | | Jump |
16 | | Jump |
15 | | Jump |
31 | | Jump |