Keyspace List for WPA on Default Routers

[Have Blue]

After looking a little bit closer at your dir-605L data, it looks to be very much in the family of the 640L
The 640L takes a hexadecimal hash, and plucks letters from them (0..F) followed by modulus 10. (Hex value % 10)
Which means that values 0..5 (and a..f) are almost twice as likely of showing up, versus chars '6789' and 'ghij' and that is reflected by the data you collected.

One thing that struck me was the prevalence of the 'b' character versus 'a' which made me wonder if zeroes are for whatever reason much less likely to be generated from whatever the 'seed' is (my assumption being that 'a' equates to '0' and 'b' equates to '1').  I had done a statistical analysis on the data, and 'b' was indeed among the most common characters.