subtract the first edge (5 sts) and the last edge (9 sts) from the total: then count the sts in the repeat and divide evenly
58 - 9 - 5 = 44 = (4 + 6 + 1 ) * Repeat 4 times
The repeated pattern is eleven stitches:
4 + 3 time ( 1 ktbl + 1 p) = 4 + 3( 2 ) = 6
Note: so long as the k1 through back loop and purl 1 are in separate stitches. Please consult pattern for description of k1tbl.
Now with pattern gauge of 58 sts / 3 sts per inch = 19 + 1/3 inches.
19.33 * your 5 sts per inch would require about 95 stitches total.
As given the pattern has k5, p4 ,(repeat 4 sections) end with p4, k5 (which gives a similar/symmetric three inch border at 3 SPI (sts / inch)
using 5 SPI you would get about a two inch border so if you want a pattern to span 19 inches total that is 15 inches of the center repeat of 11 stitches so 15*5 is 75 so 6 repeats would be 15 + 66 + 15 = 96 sts total.
You should then be able to follow their pattern and get two inch borders as you want with the gauge of 5 SPI.
I hope this helps you see the pattern repeat. I did not do a test knit to verify and am just visualizing the pattern.