This is it, verbatim:
To make this Work as useful as possible, the Editor has numbered all the stables and other out houses, likewise calculated the number of houses that probably will be built upon the unimproved lots within the boundaries before described; by which means, wherever a house is built hereafter, its number may be easily ascertained by attending to the Editor's method of numbering, which is following the course of the sun [sic] from wherever the numbers commence.All streets that cross Market-street, are numbered from Market-street, beginning at the northwest corner and ending at the southwest; other streets, lanes, &c. that run north and south, and are to the northward of Market-street, are numbered from the same corner, unless they begin at some street north of them, and do not go through the square, in that case they are numbered from the southeast corner.
Other streets, lanes, &c. running in the same direction, and southward of Market-street, are numbered from the southeast corner, unless they are bounded by a street to the southward, and do not run through the square; if so, the numbers begin at the northwest corner.
The east and west streets, &c. are numbered from the southeast corner, and end at the northeast, unless they are bounded by a street to the westward, and do not run through the square; in that case they are numbered from the northeast corner.
All houses that were empty when the numbers were fixed, and those occupied by people who would not give their names, are put down, at the end of the Directory, as empty houses, with their places and numbers.
The copy of MacPherson's directory in the Library of Congress, from which the microfilm copies of many scholarly institutions were taken, lacks this page (as well as two other pages of listings, which I had to get from the copy owned by the Historical Society of Pennsylvania).