The Beat + Bassline Editor has a default of 16 steps
For 4/4 time signature, 16 steps correspond to 1 bar or 4 beats. If we add steps, by right-clicking on the pattern and by selecting the Add Steps option, we have 32 steps, or 2 bars.
With the tempo of 140 beats per minute, one beat is 0.42857 seconds (1/140). Thus, 1 bar is 1.7143 seconds.
This is the setting of the Song Editor and Beat + Bassline Editor:
Now each block in the Song Editor is 2 bars. We select 2 beginning bars, have silence for middle 2 bars, and then select another two bars. Thus the silence is 2*1.7143 seconds = 3.4286 seconds as verified by the audio opened in Audacity: