FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
Article Id 195197
This article describes bandwidth unit differences.

1) MAX bandwidth unit is configured on mbps default.
#config firewall shaper traffic-shaper
    edit profile-Melb
    name : MS-Updates-Melb
    guaranteed-bandwidth: 0
    maximum-bandwidth : 30
    bandwidth-unit : mbps                                   <----- mbit.
    priority : medium
    per-policy : enable
    diffserv : disable
NOTE: to change the bandwidth-unit, follow the below process.
#config firewall shaper traffic-shaper
    edit profile-Melb
        set  bandwidth-unit
        kbps    Kilobits per second.
        mbps    Megabits per second.
        gbps    Gigabits per second.
2) However, when the diagnose command runs to check the shaper traffic-shaper list, see the unit in Kbytes.
# diagnose firewall shaper traffic-shaper list

name MS-Updates-Melb
maximum-bandwidth 3840 KB/sec                               <----- Kbytes.
guaranteed-bandwidth 0 KB/sec
current-bandwidth 0 B/sec
priority 3
tos ff
packets dropped 0
bytes dropped 0
So the  Configuration unit is in mbit.