Count unique values (in an ever expanding list) based on criteria

Hi all,

I have attached a dummy workbook for reference....

I have a series of record entries for ‘bottle tests’. I need a formula to provide the total number of unique entries (entries meaning the ‘bottle number’ from column A) based on specific criteria (the ‘size’ listed in column B, there are 4 different sizes).

I have tried a variety of formulas, however; they return errors or inaccurate information because it does not allow for blank cells. Also, these formulas mean that I have to filter for each one of the 4 criteria then paste to a new page in order for them to work (inaccurate as they may be…)

I need to search the range [A:A], not [A2:A1387] because the list will be updated frequently and I want the formula to self-adjust as the end-users will not be able to do any filtering, copying pasting etc..

The end result should be 4 totals:

Total number of unique bottle numbers (column A) for each criteria (column B)

Example:
336 unique entries for 38mm
210 unique entries for 45mm
Etc.

Thanks in advance for any help….