The 33 points used by NRCS* define the Dimensionless Hydrograph better than the 19 points provided in Chapter 5 of SWCE/6.

The duration of the event is 100 time units, or 5Tp. Peak discharge occurs at t=Tp=20.

The area under the curve is 2670 volume units.
Editions 3, 4, 5, & 6 of Soil and Water Conservation Engineering incorrectly gave the area as 2620 units.

The Dimensionless Hydrograph has the same total discharge as the Triangular Hydrograph (Figure 5.7 in the text). The discharge prior to Tp is 3/8 of the total storm runoff. As can be seen in Figure 5.7, that is represented by 1000 volume units. The remaining 5/8 of the storm runoff occurs in the recession limb, so it is represented by 5/3 x 1000 volume units. The base of the recession limb must therefore be 5/3 x Tp. The total storm runoff is then represented by 8/3 x 1000, or approximately 2667 volume units. The difference of 3 volume units between the Triangular and Dimensionless Hydrographs (about 0.1%) is insignificant in practical terms.

*Adapted from NRCS National Engineering Handbook Part 630 Chapter 16 Hydrographs (210-VI-NEH, March 2007).