In Excel's Histogram function, the frequency reflects the count of values that are greater than the previous bin and less than or equal to the bin number to the left of the frequency.
In other words, if you have defined bins for your data, the histogram will count all the values that fall within the range defined by each bin, including the upper limit of the bin. For example, if you have a bin defined as 10, it will count all values that are greater than the previous bin's upper limit and less than or equal to 10.