im have 0.00637 btc (16 USD) in my Exodus Wallet but
available for send only 4.28 USD.What happens ?
why are they are due so extremely high?


It's because one of the two:
1. Unconfirmed transactions you already have.
2. Fees (which means you received a lot of small/micro payments) which resulted into having a big transaction size => higher fees.