it uses as needed up to what ever the bios of the cards limit is so ?? say your card has a 8 pin and a 6 pin + board slot power is 300w
75w slot - 75w 6 pin - 150w 8 pin
with that your card maybe set for say 275w - its easier to see with a NVidia card like here for mine for a example
Board power limit
Target: 250.0 W
Limit: 275.0 W
Adj. Range: -40%, +10%
you see its a 250w card with + 10% 250 and 10% added = that 275w limit set in the bios
https://www.techpowerup.com/vgabios/178218/evga-gtx980ti-6144-150601-1
I would not worry about it not hitting the max all the time cause its going to use what it need as needed and things your running just may not be stressing it enough to need its full max power draw
then your comparing a sapphire card to your giga card ?? see may have different v-bios set parameters . your card may not be bios capable to do 200w ?
like here with this 980 ti
Board power limit
Target: 300.0 W
Limit: 425.0 W
Adj. Range: -50%, +42%
https://www.techpowerup.com/vgabios/175727/evga-gtx980ti-6144-150629-1
now see there evga 980 ti cards but notice how much evga got this one cranked up over mine ??
thing is with AMD they don't state that like NVidia cards
they don't have any rx 580 listed but like this giga rx 480 none of that info stated
https://www.techpowerup.com/vgabios/188335/gigabyte-rx480-8192-161026
now from here in this part from them
AMD Radeon RX 580 = TDP: 150 W
https://www.techpowerup.com/gpudb/2938/radeon-rx-580
from that they show its a 150w card ??
heres the giga rx 580
https://www.techpowerup.com/gpudb/b4429/gigabyte-rx-580-gaming-8-gb
same 150w , but now how much % over that is it set for to do safe ?? see it could go 200w if the cards bios allows befor any throttling occurs
your screen shot show a 150w card + 50% for a max of 225w ? see you still may not be stressing it to bang that 225w yet and may not ?
think your card is working fine and as normal
try this bench as well it got my card to max watts used [276w of my cards 275w limit +/- ]
http://imgur.com/ucfIl5K
https://www.techpowerup.com/download/unigine-superposition/
may also try that HWinfo 64 it offers good info
https://www.hwinfo.com/