the current day number

zero-origin index of the car you are currently using

number of cars in your garage

At this point you find 100 4-byte quantities.

Each of these is the base value of the car in the corresponding garage slot (see below).

These values are stored as the amount in credits, times 100. I tend to refer to this measurement as "Yen", since I believe the Japanese version of the game uses credit values which are 100 times those in the North American game. Alternatively, you can think of them as penny values.

When selling a car, you will get 50% of this value from most dealers, and 60% from the matching dealer. If this value is zero, the car cannot be sold. This happens with the B license test prize Concept Car.

Immediately after that (100 x 4 is 400, or 190 hex), you find the 100 garage slot entries describing the cars in your garage. I will not attempt to describe the meaning of those in detail here.

Each garage slot is 96 bytes long, or 60 in hex. Somewhat conveniently, this is exactly the same amount of data you see in each screen of GameShark Memory Editor.

This is the start of the space after the garage.

From about here to 8009E3AF is a bitmap representing all the parts you have purchased. I have not managed (nor really given a concerted effort) to decode the precise meaning of each entry here.

Here you can see 24 bytes of 1's, 2's, and 3's which clearly correspond to you bronze, silver and gold license cups, respectively.

The license test records are easily observed here. If you patch G.T.Gold's time at the right time, you can cheat your way to a gold medal!

These extend until about 8009E730.

Start of B license records.

End of IA license records.

Here you have 22 bytes corresponding to your best place in each of the 22 simulation mode events, including the Spot Races.

After that is a lot of weird stuff I couldn't figure out.

It looks like the Simulation Mode Time Trial Records begin here.