CONFIG_UDP_DATA_UPLOAD_FREQUENCY_SECONDS and CONFIG_LTE_PSM_REQ_RPTAU. clarification

Please clarify the following in LTE PSM mode.  Especially TAU is based on time vs frequency is 1/Time.  What is frequency second ??  Is it frequency or it is seconds in time ?  The unit of CONFIG_LTE_PSM_REQ_RPTAU is based on time.

From 

developer.nordicsemi.com/.../README.html

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