Document number are displaying with MM3F0.0 in Table ACDOCA

Hello Experts.

We have recently done the system conversion from SAP ECC 6.0 to SAP S/4 HANA 1909 On premises. We notice that the document number are appearing with 'MM3F0.0 in Table :ACDOCA after conversion. I am not sure as what does it mean and why it showing such strange number in the document number field in the table: ACDOCA

Input Parameters

Table: ACDOCA

Fiscal Year 2019

Document type : Excluding “AF”

Output.

The values other than field document number showing correctly.

Please assist to know as why The document number are appearing with MM*.

I request you to assist me on this issue, your help is most appreciated.

Regards,

Amresh.