More information can be found in this topic and in the session I/Os.
As can be seen from there, 57,263 requests have been made to ExactOnlineREST.Project.PjtTimeTransactions. Using PjtTimeTransactionsIncremental will save a lot of API requests.
Useful documentation for finding and analysing problems can be found here: Wat zijn de aandachtspunten om Power BI te implementeren?.