There aren't really any limits, and recommenders are free to answer the questions any way they see fit.
Likely they can answer some questions with just a few words, while with others they may well write 2-3 paragraphs. As a guide to your recommenders, 2-4 pages overall is a reasonable balance between readability and providing sufficient detail.
Adcom are more interested in the content, than the format. You (and your recommenders) should not stress about formatting.