It looks liek that zabbix trim doesn't work
Steps to reproduce:

• zabbix preproccessor=3
• create an trapper item(bareos.meta), type text
• create a dependent item (bareos.inc.vol.bytes), type numeric float
• Preprocessing:
  • Regexp: (?s)((Backup Level:\s+(Incremental).*)Last Volume Bytes:\s+)(\S+) \4
  • Trim ,
    send an Item:

    zabbix_sender -z <IP> -s <HOST> -k bareos.meta -o "bareos-dir JobId 32: Bareos bareos-dir 17.2.4 (21Sep17):
    Build OS: x86_64-pc-linux-gnu debian Debian GNU/Linux 9.3 (stretch)
    JobId: 32
    Job: clouddata.2018-03-14_02.00.00_08
    Backup Level: Incremental, since=2018-03-13 02:00:02
    Client: "zfs-serv" 17.2.4 (21Sep17) x86_64-pc-linux-gnu,debian,Debian GNU/Linux 9.3 (stretch),Debian_9.0,x86_64
    FileSet: "backup-zfs-serv" 2018-03-06 12:19:01
    Pool: "Incremental" (From Job IncPool override)
    Catalog: "MyCatalog" (From Client resource)
    Storage: "File" (From Job resource)
    Scheduled time: 14-Mar-2018 02:00:00
    Start time: 14-Mar-2018 02:00:03
    End time: 14-Mar-2018 02:40:32
    Elapsed time: 40 mins 29 secs
    Priority: 10
    FD Files Written: 41,668
    SD Files Written: 41,668
    FD Bytes Written: 132,529,626,952 (132.5 GB)
    SD Bytes Written: 132,539,230,807 (132.5 GB)
    Rate: 54561.4 KB/s
    Software Compression: 16.0 % (lz4)
    VSS: no
    Encryption: no
    Accurate: no
    Volume name(s): Incremental-0044
    Volume Session Id: 32
    Volume Session Time: 1520334851
    Last Volume Bytes: 132,643,422,312 (132.6 GB)
    Non-fatal FD errors: 0
    SD Errors: 0
    FD termination status: OK
    SD termination status: OK
    Termination: Backup OK"
    

Result:

Value "132,643,422,312" of type "string" is not suitable for value type

"Numeric (float)"
Expected:
132643422312