We created zero value invoices for all of these items, but set them not to go to the customer.
The positive items were all of the open deferred revenue items, set to amortize over the remaining life of the contracts.
The negative items which offset this total were set to amortize into a "manual" deferred revenue account, so would have zero impact on the P&L in future months.
Ours was a full migration onto Netsuite rather than just switching on ARM but the principle would work in the same way.
1. ITEM A. $1100 01/02/2019 - 31/12/2019
2. ITEM B. -$1100 31/01/2019 - 31/01/2019
Where item A goes to a revenue account, Item B goes to a deferred revenue account (assumes you switch on ARM for the February period, but keep Jan open to recognise the 31st Jan transactions).
Our contracts are really basic though, with well-defined recognition rules