To date, no one has authenticated Kanz Al-Umal such that someone could give you a number. However, it is well known to be full of weak reports as the author and editor (Suyuti and Hindi) did not intend to collect only Sahih Hadith. There are two ways of approaching the answer and a buffer. The first is the safe count and the second is the more realistic count. 1) Al-Albani counted when separating Jami As-Saghir 8,202 authentic and 6,450 weak reports totaling 14,652 which is 31,972 reports less than Kanz (note: Jami Saghir is included in Kanz). 2) The compiler of Mawsu'ah Al-Albani As-Sahihah (Hamza Ahmad Az-Zayn, the same Muhaddith who completed Musnad Ahmad when Ahmad Shakir died) counted 27,649 authentic reports and the complier of Mawsu'ah Al-Albani Ad-Da'ifah (Ali Hasan Al-Halabi) counted 31,577 reports, totaling 59,226 which is 12,602 reports more than Suyuti/Hindi collected. However, the largest collection of reports to date is the Mawsu'ah At-Tafsir Bil-Ma'thur by At-Tayyar who, along with a team of 41 Phds and Master students collected 85,730 reports, almost double Kanz Al-Umal. Assuming there is no repetition in the Tafsir, there are 26,504 reports more than what Al-Albani commented on and 39,106 more than Kanz.
Al-Albani counted when separating Jami As-Saghir 8,202 authentic and 6,450 weak reports totaling 14,652 which is 31,972 reports less than Kanz (note: Jami Saghir is included in Kanz).
The compiler of Mawsu'ah Al-Albani As-Sahihah (Hamza Ahmad Az-Zayn, the same Muhaddith who completed Musnad Ahmad when Ahmad Shakir died) counted 27,649 authentic reports and the complier of Mawsu'ah Al-Albani Ad-Da'ifah (Ali Hasan Al-Halabi) counted 31,577 reports, totaling 59,226 which is 12,602 reports more than Suyuti/Hindi collected. However, the largest collection of reports to date is the Mawsu'ah At-Tafsir Bil-Ma'thur by At-Tayyar who, along with a team of 41 Phds and Master students collected 85,730 reports, almost double Kanz Al-Umal. Assuming there is no repetition in the Tafsir, there are 26,504 reports more than what Al-Albani commented on and 39,106 more than Kanz.
Given the figures we can speculate that there are at least 8,200 authentic reports in Kanz but closer to 27,600 and there are at least 6,400 weak reports but closer to 31,500 with a buffer of 26,500 to 39,100 wiggle room between them. Its possible to authenticate the Kanz using the Mawsu'ah Al-Albani As-Sahihah and Mawsu'ah Al-Albani Ad-Da'ifah with 12,600 reports to spare.