20 gallons in 25,000 is more than a 1000 to 1 dilution. That will probably result in a negligible bromide/bromine amount. However, it's not based on your bromine level, but your bromide bank and that could be high if you not only added sodium bromide initially but also used bromine tabs. Even so, it's probably not more than 100 ppm so after dilution into the pool would be around 0.1 ppm.
Bromide goes away only through water dilution, similar to other salts. Bromine can outgas from the pool somewhat, though does so more slowly if you've used bromine tabs since they add DMH that acts somewhat like CYA if the concentration gets high. Bromine can form organic bromamines that may get filtered out in some cases. However, you can't really count on these methods of reduction as they could be very slow.