The steam indicates tens and ones. The leaf indicates the tenths of each weekly sales.
From the table, the steams are:
57
58
59
61
62
To include the number 58.80 into the plot, we have to put an 8 on the leaf column next to the 58 row. Similarly, to include 59.5, we have to write a 5 next to the 59. Applying this procedure to all data we get:
Steam | Leaf
57 | 5
58 | 8
59 | 3 5
60 |
61 | 8
62 | 0 3 8