The wedding cloth is knit from the bottom up in the sense that you have the pattern for letters, knit bottom up, then the pattern for the heart, knit from the point up and then another section of letters. Finally there is another section which will be at the top and is I think, the wedding rings. Using the direction of the heart as a guide, the letters are knit from the bottom up.
That said, the pattern won't look like the one pictured. The heart will be in stockinette against a garter stitch background. I'm not sure how well the letters will stand out on that kind on background.
You might try knitting a few letters just to see whether you like the result.