The on computer dive log and the downloadable dives are separate and unrelated.
The on computer log will always simply have the most recent 24 dives. The dives in the on computer log will be numbered consecutively, as long as there is less than 24 hours between dives. If more than 24 hours passes, a new series, starting at 1, will be started. All of the previous 23 dives are still in the log. For example, I recent did 18 dives on a visit to Florida. I did 2 dives, had a day off, did 12 dives over 5 days, had a day off, and finished with 4 more dives over the last 2 days. So for these 3 series, they are numbered 1-2, 1-12, and 1-4. They are all in the computer log, along with 6 other dives, for a total of 24. The on computer log has simple information on 4 screens, date, start time, dive number, surface interval, max depth, dive time, water temp, ending O2 exposure %, max pO2, and gas used.
Here is a screen shot from OceanLog showing the download screen. There are 58 dives/ about 60 hours available for download using the 30 sec sampling period. I have never used 2, 15, or 60 second sampling, but assume it would affect the number of dives available for download based on the amount of data. This seems to be confirmed by
@RIHappyDiver in post #15. Perhaps others, using different sampling rates, can further substantiate this.
The 3 series of dives from my recent visit to Florida can be seen below, with the same numbering system that is used in the on computer log
View attachment 509344
The downloadable log contains more information as seen from the example, below. This happens to be the last dive in download list 2/28/19, #4. As this computer is AI, gas use, SAC, and RMV are shown, but would not be included with the Geo 4.0. The dive profile is also included (the red area in this profile is a few minutes of deco). Obviously, the exact information in the download is dictated by the log application you end up using.
View attachment 509347 View attachment 509348
I hope this clears up your questions.
Good diving, Craig