I got about 3.5 yd of dark and 5 of light..
Ill walk through the calc with you so you can verify my assumptions...
You want to make a quilt 7 blocks by 8 blocks,,, so 7 x 8 = 56 blocks
Your post gives the cutting directions for two blocks, so I divided 56 by 2 = 28.. 28 times the number you quoted in your post should give you the requirements.. so here goes.
You need 3 of the dark and I rounded the size up to 7 for easier calc.
Assuming your fabric has 40 usable inches, divide 40 by 7 = (5) 7 inch squares across the width of the fabric.. so, divide the total number needed (3 x 28 = 84) by 5 = 16.8 or 17 strips, 7 inches wide..
17 x 7 = 119 divided by 36 (inches in a yard) = 3.3 yds,, I round up to the nearest 1/2 or 1/4 yard, so I would get 3.5 yds
For the light you said you need (1) 7 inch and (1) 13 inch for 2 blocks so we will follow the same calc..
28 / 5 = 5.6 or 6 stips 7 inches wide or 42 inches
28 / 3 = 9.3 or 10 strips 13 inches wide or 130 inches
130 + 42 = 172 inches / 36 = 4.7 or 5 yds if you round up