Fsbuild-2 Flight Planner

I generated a flight plan from EGNT (Newcastle) to GCTS (Tenerife South) using STAR KO3DCG. My cruise level is FL280. When I look at the Navdata chart that corresponds to this STAR (KONBA3DCG) I see that the chart flight level between GURKA and BRICK is FL90 but the FSB flight plan still shows FL280. The same is true where the chart shows FL70 between BRICK and ARACO but the flight plan still shows FL280. There are similar disagreements until you get to BAME where the chart shows 6000 and the plan shows 5000. From the viewpoint of descent the chart seems resonable. I am not particularly experienced at STARs. What am I missing?

Does that mean that it is simply following the STAR route but can be considered just part of a usual IFR approach? My problem has been that I have tried flying this approach twice without considering it as part of a STAR (no FMC) and ATC has brought me in at too high an altitude. Should I edit the flight plan to change the altitudes?