Quantize Notes dialog quantize all selected notes relative to bar line positions.
The Quantize Notes dialog is brought up by selecting the menu item "Edit->Quantize...".
Quantization Step is measured in note duration units, ranging from half note to 32th. It should divide measure size.
Quantize Onsets - if checked, quantization is applied to note onsets. Note durations are preserved.
Quantize Ends - if checked, quantization is applied to note ends. Note onset positions are preserved.