使用xlUp得到奇怪的结果

I have a column with numbers in it, starting at row 25. I want to fill an array with the row numbers for which this column has data. The following code works provided the numbers are arranged in rows that are far apart. I have assumed no more than twenty such rows exist within a 500 row range for simplicity. When rows are consecutively filled with data I get strange results. For example: on rows 45, 46, 47 there is data and yet this code returns only rows 45 and 47. I am new to VBA and am easily disheartened. Please help :)I have a column with numbers in it, starting at