This is written below the page:
For legacy, the virtual size and size will be the same since all of its data are all non-Witness.
You might be missing the point of "n sat/vByte", it's as simple as this, example:
3sat/vB of a SegWit transaction with 134 vBytes size. Just multiply it and you'll get the total fee of your transaction = 402 satoshi.
2sat/B of a Legacy transaction with 235 Bytes size = 470 satoshi.
In this case SegWit transaction will be prioritized over the Legacy transaction even though it has lower virtual size and lower total fee since it's paying a higher fee rate.