A slur links two notes running (warning!), identical each other (for pitch and not for length). It is generally used in place of dot or when the note has to last longer than one measure.
The C for the left hand in the first bar lasts for five movements. Why? Because semibreve (4 movements.) and crotchet (1 movement) are linked by the slur. That sign, starting from the first bar C up to the C of the second one, is the value slur, not to muddle up with the portamento slur. The two notes join together and their values add up: 4+1 = 5. The execution will be ongoing, i.e. the key is to be pressed one time only! It isn’t lasting for four movements anymore, but five. In order to understand as better as possible this concept, I suggest you to glance at the video.
As already said before, these exercises revive the technical difficulties of the previous ones. Really soon, you will be able to play your five fingers favourite piece. See you next time!