Hi,
Can a subscription have multiple active promotional offers at the same time? If so, what is the resulting behaviour?
Some of the documentation says a subscription can have up to "10 active offers per subscription", but then there is another place where it says "A user can redeem and have active only one promotional offer at a time."
Can provide the source of the info above if required
Correct, as a developer you can configure up to 10 Promotional offers per product and active at any given time. This allows the developer to configure different offers with terms that are tailored and personalized to fit the customer cohort you are targeting. So one offer may be to encourage existing customer to upgrade while another offer could be focus on winning expired customer back to your server.
As for the redemption of offers, customer can redeem a given promotional offer as many times as you choose to offer them but a customer can only use an offer one at time. Accepting new offers will either take effect immediately or at the next renewal period.