Let me explain my question.
There are numerous instances of double consonant letters in Russian. More specifically, I mean double consonants in loanwords. Sometimes they denote a geminated (long) consonantal sound. Like in масса, касса, брутто, ванна — you pronounce the long sound [мас:а], [кас:а], [брут:а], [ван:а]. Other case is that you write a double consonant but pronounce it as a simple, non-geminated phoneme. Examples: баллон [балон], аккорд [акорт] and so on. In both cases, the combination of two identical consonant letters in a row denotes a single sound.
For comparison, combinations like НЬ, ЛЬ also denote one single sound. E.g. коньки = [кан'ки], мальчик = [мал'ч'ик].
When dividing words between lines, you cannot split it as кон-ьки, мал-ьчик. On the other hand, you MUST split as follows: мас-са, кас-са, бал-лон, клас-сный, програм-мка.
- В словах с двойными согласными одну букву оставляют на строке, вторую переносят на другую строку: Ан-на, суб-бота.
I wonder: is there an explanation for this rule? Seems to be very illogical.