A slope of +0.6 means that (on average) Y changes +0.6 when X changes by +1. The correlation coefficient (ρ) simply tells you how close the (X, Y) points plot to the regression line: if ρ is near +1 or -1, then the points lie very close to the regression line; if ρ is close to 0, then the points are scattered far from the regression line.

Correlation 1 means: When a variable moves by 1 standard deviation in one direction, the other variable also moves by 1 standard deviation in same direction. (nothing to do with slop)

Now if variable 1 has standard deviation of 1 unit and variable two has standard deviation of 0.6 unit, the slop can be 0.6 or 1.67 based on which axis you plot your variables.