Thanks for designing MTP. It has changed my trading life!
Russ, Private Trader
If Wave (3) is the extended wave (i.e. it is the longest Wave) then very often Wave (1) and Wave (5) tend to be approximately equal in price.
As wave (5) is very often equal in price to Wave (1), once Wave (4) is complete, this allows an easy way to approximate where the Wave (5) will end.