It means that for every watt of power you consume, you produce 0.45 Sols of hashrate.
Sols make your revenue. Power is your cost.
If your biggest expense is watts (power bill), then maximizing Sols/watt will maximize your revenue after accounting for your power bill.
You can play with raising/lowering each aspect. If you find something that raises sols without raising power draw, good! (more power, same cost) If you find something that keeps sols but lowers power draw, good! (same power, less cost)
But if uses more power without making more sols, bad!
The Equihash algo is very memory-intensive, so output is more sensitive to Memory settings to Core settings. Core clock tends not to affect output very much, so we can often reduce core clock to save power without hurting Sol production. Speeding up the memory often leads to more Sols… but that increase speed also uses more power. Is it worth it? Use the ratio… if Sol/Watt is higher, then it’s an improvement. (As long as you don’t burn up your equipment with the heat!)