10.2C7 is not the same as Cmaj7

This distinction is essential.

Cmaj7

C E G B

C7

C E G B♭

Only one note differs:

B versus B♭

But the function changes dramatically.

C7 means a dominant seventh chord.

Formula:

1 3 5 ♭7

So:

maj7 means major triad + major 7th plain 7 means major triad + minor 7th

This notation surprises many classically trained musicians.