Number Sequences

 There are various setup that you may achieve with the number sequences.

Lets get in to detail on what functionalities we may use.

Which parameters you can setup in a number sequences: 

On number sequences, you may define various parameters;

• You can setup number sequences as continuous.

In case of unexpected issues occur, system cannot recycle numbers automatically for continuous numbers. Run the cleanup process to recover the numbers.

• You can set up pre allocation for performance, so number sequence will be allocated for use.
• You can setup constant figures for smart coding.
• You can define legal entity information for smart coding and it makes easier for reporting purposes (For consolidation etc.)

Number Sequences on journals: You can create several journal names which have different number sequences. So when you post a journal and check from the voucher transactions, you know which type of transaction is being posted.

Number sequences with date: You can setup a number sequence to be used within a date interval.

Number sequence groups: You can use the number sequence groups to differentiate numbers per processes. For example, if you select a number sequence group on an SO or PO, the invoice number can be differenciated per those PO or SO. Foe example you know which orders are internal and external directly looking at the number.

Use same number sequence: You may use the same number for similar process. For example, for better tracking, you can use the same number for the sales order invoice and its voucher. This applies not in all type of number sequences but for some specific processes like invoices and their vouchers.

Vendor Group Number Sequence: You can assign number sequences to vendor groups. 

I think what would be good is to have the number sequence setup for the item groups as well.

You may find details for number sequences from the link below:

https://docs.microsoft.com/en-us/dynamics365/fin-ops-core/fin-ops/organization-administration/number-sequence-overview