CREATE TABLE table_3873 ("Game" FLOAT, "Date" TEXT, "Team" TEXT, "Score" TEXT, "High points" TEXT, "High rebounds" TEXT, "High assists" TEXT, "Location Attendance" TEXT, "Series" TEXT)

What is the series number when al horford (10) had the high rebounds?
SELECT "Series" FROM table_3873 WHERE "High rebounds" = 'Al Horford (10)'
SELECT "Series" FROM "table_3873" WHERE "High rebounds" = 'Al Horford (10)'