Spreadsheet anomaly read

Read the attached file. Do not analyse it yet. Tell me what is wrong
with it first.

Start with structure. Rows, columns, the header row you used, and one
line per column: what it appears to hold, its type, how many cells are
empty, and how many distinct values it has. Say which column you think
is the key and why.

Then anomalies, one row each:

  What. The problem, named plainly.
  Where. The column, and the row numbers or a count if there are many.
  Example. Two actual values from the file.
  Why it matters. What an analysis would get wrong if nobody noticed.

Look for at least: duplicate keys, mixed types in one column, dates in
more than one format, numbers stored as text, trailing spaces, values
that should be in a fixed set and are not, totals that do not match the
rows above them, gaps in a series that should be continuous, and values
outside a range the column's own meaning allows.

Then two sections.

What I assumed. Every assumption you made to read the file at all: the
header row, the date format, the decimal separator, which sheet.

What I could not check. Anything that needs a source outside this file,
including whether the extract is complete and whether the period is the
one I think it is.

Rules. Do not clean, correct or reshape the data. Do not compute any
business metric from it yet. Report on the file as it is.