Once a subscription is unpaid rather than active, the amount does not count towards your MRR. If you mark subscriptions as unpaid as your dunning final action, we consider a subscription to be delinquent at the time when the subscription transitions to unpaid.
Delinquency is considered differently in 2019 than it was in 2018. If you are looking at year-to-date data that includes subscription data from 2018, note that subscriptions were only considered delinquent when the following invoice was generated and automatically closed due to delinquency. As of 2019, Billing considers subscriptions as being delinquent as of the date that the subscription was marked as unpaid, rather than the generation date of the next invoice.
In 2018, if you had your final payment attempt on the 8th but didn't bill until the 15th of the month, the subscription would be marked delinquent as of the 15th. In the new system, as of 2019, the subscription would be delinquent as of the 8th.