Some lines of gurbani are repeated - some even a few times. For example, in Japji Sahib, the following line occurs 4 times
NANAK BHAGTA SDA VIGAAS SUNAIR DUKH PAAP KA NAAS
So to be able to memorise Japji Sahib, it helps to know and remember where these repetitions occur. In the same way, there are repetions in Sri Jaap Sahib too. The document below helps to show the repetitions in Sri Jaap Sahib and knowing them helps to memorise Sri Jaap Sahib.