The system measurement box shows the length of the acquisition buffer as well as the sample rate. Right now that is 2.62ms and 100MHz. Given the memory of 4M samples, we can acquire up to 40ms without subsampling (4M samples / 100M samples per second). However this is not enabled by default as it would slow down the data refresh rate. By default the acquisition buffer is twice the size of what you see on the grid. I open the acquisition overview buffer by pressing V. The viewport is moved around by dragging the highlighted part. Moving the trigger is done by dragging the shaded part...