DA10 flight crew on CSHEL ONE RNAV SID out of RSW levels at 530 ft vice 4000 ft MSL based on misreading of Government aero chart symbology.

Narrative

After using commercial charts for over 30 yrs we recently changed to the Government charts and on departure at RSW the CSHEL procedure called for a climb to 530 ft. It seemed low to both of us but since the FMS had the same altitude limit we accepted it as the climb limit for the procedure. Assuming that departure control would give us a higher altitude very soon after departure. What the first officer failed to see was the 'thence...' part of the departure procedure and since the FMS did not have something different I did not question further the low altitude limit. Shortly after departure the low altitude limit was reached and ATC was busy with other traffic so we leveled off until issued a climb from departure. Both of us at that time felt that something was not correct. After some quizzing of ATC we found the 'thence...' part of the departure procedure and realized that we just plain missed the climb portion of the SID. Our personal system of checks and balances broke down when we did not dig further for an answer to both of our concerns that the initial altitude was too low. Fortunately the weather was better than 5000 and 5 so there was no danger of CFIT just a bruising of our egos for not catching the obvious. I believe that several factors came together to cause this miss-understanding. We have been flying together as a crew for 16 yrs so we have learned to place a great deal of trust in each others capability. We switched to the Government charts and while the information is there it doesn't always 'jump' out at you because of experience in using a different format. Callback conversation with reporter revealed the following information: Reporter confirmed they had taken off on Runway 06 and had failed to mentally connect the ellipsis at the end of the Runway 06 text with the ellipsis preceding the cleared altitude text which followed the Runway 24 procedure. Reporter also noted the altitude 'underline' didn't immediately cause him to question its meaning because underlines are used elsewhere on the chart merely for emphasis; i.e. under the departure transition names. Reporter reemphasized the impact of the different format from that used for many years previously by himself and his co-pilot; stating it has required some concentrated study of the Government symbol legend to familiarize the user with such subtle differences.