[Handbook] How do we contribute towards the profitability target for support?

In the support team handbook landing page, there is a mention of long term profitability targets:

The long term profitability target for support is 90% gross margin.

UPDATE: The FY20 Financial Planning Goals state that Customer Support expenses should be 10% of annual recurring revenue.

This begs a few questions:

• How do we calculate the gross margin? What are the revenues and what are the costs?
• How can support team members and support managers actively contribute towards this target?
• How far in the future is "long term"?

/cc @gitlab-com/support/managers