Having read two of his books, seen many of his vids, having been a meditator for 30+ years, and authoring a page on nonlocal consciousness and perception, I feel my answer will help.
The short answer is that he wants you to temporarily abandon your usual thought based in language, and to instead focus on your perceptions of space, both large and small. Language limits your experience. By space, I take him to mean to...
1.) focus only on your perception of space without trying to describe it. To stop thinking and stop explaining things to yourself. Descriptions will always fail in an exercise like this. Language and common mentation are not reality. They are representations of reality, and often inadequate ones.
It's your personal experience of everything and nothing which will light you up, and, once one is practiced at that, you achieve a far different perception of reality. Most people's minds are like their Beagle barking incessantly in the middle of the night. Like hyperkinetic monkey-mind. Unless you manage your monkey-mind or barking Beagle mind, they keep you stuck in an unproductive thought based in the past, in story.
2.) to also consider the thought, in the context of your experience, that new and joyful things will occur to you once you distract yourself from your regular emotional and thought patterns. New and joyful things occur to people once they stop trying to weave a story about what happened. He wants to put us into the moment, which allows us to live into the future we imagine.
Helpful?
I have several guided meditations by Dr. Dispenza. During the open focus part of the meditation on the body parts, he'll say something like, "can you feel the energy between your ears IN SPACE?" (emphasis mine).
What does he mean by "in space"?
I can agree partially with these points, however, as an experienced meditator I know them to be too cognitive. Perception is something to be removed as well, as physical perception could make the sit uncomfortable. This does not happen in the earliest stages of meditation.
One only needs to first relax, become calm, and become detached from the body. In the earliest stages of meditation I found it best to select a meditation object, something that one may find to take the entirety of attention. This is the way a meditator becomes detached from to body. In Vipassana meditation, they use the breath (not advocating this, only using as example). The point becomes that as you relax and calm intently focused up your meditation object that your awareness begins to expand. One may start to notice that they are capable of viewing a thought as it arises, but still intently focused upon ones meditation object, they realize that the thought is separate from oneself, and I believe the above did a good job in adding perspective into this.
Slowly one may observe a subtle sensation arise, likely in the hands or feet. It feels like static, or minor vibrations, or like the brush of a cats fur. This sensation is subtle, still intently focused upon ones meditation object one drifts. A thought arises but one continues to drift and the thought falls away. Soon this feeling may return, a subtle tingle within the hands or feet. At this time the meditator makes this subtle sensation the meditation object and continues.
I have not read Dr. Joe's books. I was doing internet searches lately and came across an individual that I knew to be having a religious experience, and so I reached out to him. Without presuming too much, the term "in space" could be a reference to awareness. Awareness being the withdraw inside oneself and being present in the moment to what is there. If one has an itch on the smallest toe of the right foot, one knows they have an itch on the smallest toe of the right foot. This state of being aware of specificity, although not cognitively, but experientially, I could see as "in-space", or awareness.