My post about bit fields was basically about information theory: 7 letters from A-Z has a certain number of bits. Which is to say, the quantity of "information" you can store in it. The number of bits is the log2 of the number of values. Thus, 0-7 (or 1-8, or 156-163) requires log2(8) = 3 bits.
If you have a variety of different values you want to be able to encode, each of which requires a certain number of bits, then you can compare the sum of required bits to the available bits and see if they fit.
Now, that assumes that all of the values are independent: if I have 8 of value A and 10 of value B and 123 of value C, then if you can generate all combinations with equal likelihood, then you need log2( 8 * 10 * 123) bits to hold the "information" for those three values. You can come up schemes to extract those three fields from a smaller number of bits, but only if they "share" some bits, which means that not all combinations of the three variables can be encoded.
I suspect that some of the variables for Spacegate really are independent but some of them overlap. For example, the type of animals and their hostility has 7 values (none, simple, hostile simple, complex, hostile complex, anomalous, hostile anomalous), taking slightly less than 3 bits (although for simplicity, I might encode it with (none, simple, complex, anomalous) - 2 bits and (peaceful, hostile) - 1 bit). I expect that any of those combinations can appear with any comparable combination of plants. I.e., they don't overlap.
But do they store the image # of plants, animals, aliens in separate fields? Or is there a single field which is mod'ed by the number of images for the particular type? Or is there some other way that info is overlapped with other data? Who knows?
I think the best way you can contribute to the spading is to publish your discoveries, either on the G-D thread, or in the spading spreadsheet, and let those who are interested in crunching the data go and crunch it.
It will take lots of data to decide which values really are independent - every combination is possible and is equally likely - and which overlap with which.
As I said, I was theorizing, rather than, really, spading.