Set Keyframe Time dialog wrong time display issue

When editing the time of multiple keyframes using the 'Set Keyframe Time' dialog, the dialog will show wrong keyframe time if the time of the min-keyframe goes below zero. It does that to prevent time from going below zero. But this causes confusion if the user continue the edit the time after that.

Steps to reproduce:
1. create a presentation with 2 or more key frames with different times (can be in 1 object or more)
2. multi-select 2 or more keyframes
3. double-click the keyframe with max time from the selection
4. set the time to a value that makes other keyframe(s) in the selection go below zero

result:
The min-time keyframe time is set to zero, but now the dialog doesnt show correct keyframe time for any future edits till the dialog is closed.

expected result:
The min-keyfram time is set to zero, but the dialog should show the correct time for the pressed keyframe.
Additionally a highlight for the pressed keyframe would be nice (a yellow circle around it).