Understanding the GSM specs

Hello friends, I want to modify the SYSTEM INFORMATION data, but I have some difficulties to understand the GSM spec. It's about the GSM 04.08 part 10.5.2.34, I don't know how to interpet table 10.5.72 (and other similar tables). According to paragraph 9.1.35 table 9.32 (GSM 04.08) SI3 rest octetets has a length of 4 bytes, but according to par. 10.5.2.34 we're dealing with a type 5 IE and thus with length of 5 bytes. That's odd to me, but hey, the world is full of surprises :) Anyway, the problem is I don't know how to interpret table 10.5.72 (of GSM 04.08). I mean, for example, element CBQ (Cell Bar Qualify) is at bit 1. Bit 1 of what, which octet? What is L | H? Can someone explain it to me, so I can experiment with SI messages? Thank you!