I tried looking into a file by using this code in a Numeric Display or parameter field. I also tried to convert the sample position into 0 to 1 range for use in SampleStart and so on, by dividing the sample fileduration in samples, but it doesnt seem to be calculated properly... investigating.
A little perusing of the Kyma X Revealed Smalltalk appendix reveals sampleFrames and so this is the final correct code to extract Marker positions and normalise them to (0,1) range.
You can remove the self debug once you are got it clear whats going on inside the collection.
| filename markerSamplePosition |
filename := 'aFileWithMarkers.aif' asSamplesFile.
self debugWithLabel: 'Names and sample positions of the Markers' value: (filename markers) .
markerSamplePosition := !Marker of: (filename markers values asSortedCollection).
markerSamplePosition / (filename sampleFrames)