I loaded a log cabin block in EQ7 that measured 7.5 inches. A layout of 7x8 blocks with a 1/2 inch binding on each side showed a finished size of 54x62. Then I asked EQ7 to give me fabric yardage. The result was 5 yards. EQ7 does use 40 inch as the fabric width and sometimes this can overstate fabric needed. At the very least, I would estimate that your quilt would take about 4.5 yards.
Edited to add: Keep in mind that every seam in that quilt uses 1/2 inch of fabric and there are a lot of seams in any log cabin.
2nd edit: Thanks to bearisgray for the reminder about the backing and batting. You used a lot more than the yardage that you originally calculated. I would have used about 2.5 yards for the backing. The binding has been included with the block yardage. So, my unverified, but best guess, is 7 yards of fabric for the blocks, backing and binding.
3rd edit: And here is the back of the pattern stating yardage and it looks to be about 8.3 yards.
https://www.shabbyfabrics.com/Waterm...rn-P51660.aspx