The default? So it's not Electrum's calculation at fault.
There's a slider and it will be set to whatever you've used in your previous transaction or if you haven't done any transaction yet: within 5-blocks ETA (not priority).
But the number of added unconfirmed transactions is higher than the rate of mined ones, it'll get buried deeper until that ratio flattened.

Try to add it to viabtc's accelerator on the next "o'clock" (I'll try to add it myself, but don't count on it).
Luckily, your transaction's sat/B reached 11.9sat/B so it'll be accepted by their free accelerator.
Also, an accelerator needs to mine a block first to be able to include your transaction, it doesn't work in an instant.