I think something needs to be cleared up.....
1. Standard tuning
refers to the guitar being tuned to EADGBE.
2. 440Hz refers to the A note being tuned to this frequency and all other notes are relative to it.
A440Hz is the standard tuning pitch
probably used by 95% of guitar players. There are other tunings, of course.
Make sure that your tuner is set to 440Hz. The tuner will take care of the notes EDGBE automatically as it will use the A440Hz as a baseline/reference.
The other notes (EDGBE) will all have different frequencies to A and to each other. That's what gives them their pitch relative to A.
Here's a link:
And as a correction, it's not standard E.
It's just standard tuning.
In fact, it's based around the middle C from the piano, as the piano has been around a lot longer than the guitar. However, the A note (middle) on the piano is still 440Hz and the piano is/was **usually** tuned from the A note first, using a tuning fork. Today, electronic tuners will most likely be used.
Correct me if I'm wrong.....