The day formula stored for this lot is Ascendant plus the Lot of Fortune minus the Lot of Spirit. Both underlying lots contain the Ascendant, and by day Fortune is Ascendant plus Moon minus Sun while Spirit is Ascendant plus Sun minus Moon. Substituting both and cancelling gives Ascendant plus twice the Moon minus twice the Sun.
So Basis keeps exactly one Ascendant, which is what one might expect, but it carries the Moon and the Sun at double weight. That is the arithmetic behind the doctrinal description of it as the point where Fortune and Spirit are combined: the two Ascendants of the underlying lots cancel to one, and the lunar and solar terms reinforce rather than cancel.
Its motion is the Ascendant's plus a little. Twice the Moon is about 26 degrees 22 minutes a day and twice the Sun about one degree 58 minutes, which together add roughly 24 degrees to the Ascendant's full circle. The lot advances one degree every three minutes and forty five seconds, slightly faster than the Ascendant itself, so it needs a birth time recorded to the minute in the same way the Ascendant does.
There is one further property worth noting. Because the Moon and Sun enter at double weight, the distance between Fortune and Spirit in a chart, which is twice the elongation of the Moon from the Sun, is also the distance from the Ascendant to Basis. The lot sits at a lunar phase angle measured out from the horizon.