These tablets are part of the Cuneiform Sylabary B from the second millennium, texts made to teach reading and writing in the Sumerian language found in presumably private schools in residential areas of Nippur and Ur.
After TU TA TI TUTATI comes NU NA NI NUNANI, and so forth, presumably to be read aloud in class while practicing writing.
This "TU-TA-TI" instructional text was studied in all the languages that used Cuneiform and found in the archaeological remnants of many cultures.
[3] According to Steve Tinney from Penn Museum, the TU-TA-TI text, used for studying pronunciation, had more than 80 syllables and was followed by a list of names to read and write.
There are a total of 44 sequences at most in any of the artifacts, which means 132 types of signs and therefore syllables, 176 examples to read and write, with a 264-letter count.