Hi Lindsay,

By selecting all scans I meant the complete time series. 
This can be done by using the filter option in SPM and setting it to 1:1000. This way you can select every scan in your time series. 

In my case:

exampledata.nii,1
exampledata.nii,2
...
exampledata.nii,499
exampledata.nii,500

Hope this helps?