Details of the MBC can be found on http://www.deborda.org/faq/voting-systems/what-is-a-modified-borda-count.html
When subjects are very complex, the consensors should try to ensure that the maximum number of options on the final ballot paper is 6.
If the matter is relatively simple, or if those involved are doing a prioritisation or shopping list, then more options can be considered.
If the number of options on the ballot is < 10, the voters may be asked to complete a full ballot of all 10 preferences. If the number is > 10, then voters may be advised that only 6 preferences are required, i.e., a full ballot consists of 6 preferences.