The lookup table together with the IRQ routine allows you to set Port1 with its 8 output pin (P1_0, P1_1, P1_2, ... P1_7) to any value with a time resolution of 0.1ms and a cyclic repetition of the pattern every 18 ms.

Maybe it helps to think of it as a kind of a (arbitrary) binary function generator with 8 outputs, fixed 0.1ms resolution and fixed pattern length of 180 entries.

Taking
servo(12,10,15,14);
of your posted code as example.

You'd want to setup the table so it gives you

0x0f,  /* 0.0 ms: pin0=1, pin1=1, pin2=1, pin3=1, pin4..7= 0 */
0x0f,  /* 0.1 ms:                              same          */
0x0f,
0x0f,
0x0f,

0x0f,
0x0f,
0x0f,
0x0f,
0x0f,

0x0b,  /* 1.0 ms: pin0=1, pin1=1, pin2=0, pin3=1, pin4..7= 0 */
0x0b,
0x03,  /* 1.2 ms: pin0=1, pin1=1, pin2=0, pin3=0, pin4..7= 0 */
0x03,
0x02,  /* 1.4 ms: pin0=0, pin1=1, pin2=0, pin3=0, pin4..7= 0 */

0x00,  /* 1.5 ms: pin0=0, pin1=0, pin2=0, pin3=0, pin4..7= 0 */
0x00,
0x00,
...    /* another 162 zero's following here */

 

when the table contents are read and fed to P1 with:
P1 = table_P1_over_time [ ms_tenth_countdown ];

(Note, I used a countdown to index the table so the compiler could later make use of the compact djnz instruction)