A single beat can be divided into a number of divisions. The default is 120, so each beat has 120 ticks, or 60 ticks for an eighth note, 30 for a sixteenth note. However when you record a midi part in this also means that each piece of data is getting slightly quantized to the nearest of the 120 ticks for that beat.

This 120 can be adjusted in Options - Resolution to much higher numbers for a greater degree of accuracy.
A lot of users don't understand that this 120th division also comes into play for audio editing. Since RB uses the measure-beat-tick setting to select the from-thru section the most exact you can get is the nearest 120th of the beat for an audio edit if left to default. If you go to the larger resolution numbers you can edit almost down to sample level.

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