Here's one transaction sample, this will display if you click "preview" after selecting the fee rate (minus the edits):

• The "2.1 sat/vbyte" on the left is the fee rate I picked in the previous window's sider.
• The "141 vbytes" on the right is the transaction's computed virtual size based from the number of listed Inputs and Outputs regardless of each's values in BTC.
  More inputs in the list will result with significantly higher size while more outputs will slightly increase it. (different address types also result with different sizes)
• So, since the "fee rate" is in "satoshi per virtual bytes", you'll multiply it with the transaction's "virtual bytes" to get the absolute fee.
  That's 2.1 x 141 = 296.1sat or 300sat (0.000003BTC) rounded-up.

Now, check the transaction details in your transaction history by double-clicking the dates.

Here's one transaction sample, this will display if you click "preview" after selecting the fee rate:

• The "2.1 sat/vbyte" on the left is the fee rate I picked in the previous window's sider.
• The "141 vbytes" on the right is the transaction's computed virtual size based from the number of listed Inputs and Outputs regardless of each's values in BTC.
  More inputs in the list will result with significantly higher size while more outputs will slightly increase it. (different address types also result with different sizes)
• So, since the "fee rate" is in "satoshi per virtual bytes", you'll multiply it with the transaction's "virtual bytes" to get the absolute fee.
  That's 2.1 x 141 = 296.1sat or 300sat (0.000003BTC) rounded-up.

Now, check the transaction details in your transaction history by double-clicking the dates.