The graph shows the flyby geometry in the aerocentric (inertial) Mars mean equator and IAU vector of J2000 (the IAU vector at Mars is the point on the mean equator of Mars where the equator ascends through the Earth mean equator; this vector is the cross product of Earth mean north with Mars mean north).
Also shown are Phobos and Deimos.
The altitude (shown in km as "h= ..." when you hover the mouse over a point) is calculated above an ellipsoid with an equatorial radius of 3396.19 km and a polar radius of 3376.2 km.
The popup label also shows, in km/s, the aerocentric speed (Vmar) and the heliocentric speed (Vsun) of the spacecraft.

The orange line represents the Mars heliocentric velocity vector, while the yellow line points toward the Sun (both lines lie near the plane of the ecliptic).

According to the NAIF's files, the change in the velocity vector was 2410 m/s.

The values obtained for the periapsis are:

	time: 2007-02-25 01:57:59.279 UTC
	radius vector: 3648.084 km
	aerocentric speed: 10.0533 km/s
	location: 43.8332, -60.9076
	altitude: 261.413 km

The minimum distance between Rosetta and Phobos was about 4621 km.

Here's the distance between the spacecraft and Mars (blue plot) and the spacecraft speed wrt the Sun (orange plot).
The green vertical lines represent the Mars sphere of influence (the distance from Mars where the gravitational acceleration of Mars and of the Sun are the same).

The particular geometry of the flyby decreased the spacecraft heliocentric speed from about 24.1 km/s before the SOI to about 21.8 km/s after the SOI (the heliocentric speed of Mars near the flyby epoch was about 25.4 km/s).