Lab tests may be expressed in different units.
Sometimes the numbers change and sometimes they are
interchangeable.  Bottom line is, compare your results
tested at a given lab with THEIR reference ranges
(sometimes called normal ranges).  The mcg/dL stands
for micrograms per deciliter.  The ng/dL stands for
nanogram per deciliter.

Serum creatinine is a common test to measure kidney
function.  Your levels (0.9 mg/dL) are fine.

Automated Differential:
A total WBC count is done, then a "differential" is
done to see how many and what kind of WBCs are
present.  There are two ways of performing a
differential: manual, where a drop of blood is put on
a slide, spread out into a thin layer, stained, and
then someone actually looks at the blood smear under a
microscope; or automated, where the instrument that
does the rest of the CBC (complete blood count) counts
how many there are of each type of WBC.  Automated
diffs have become very reliable.  The numbers you
posted are absolute counts, obtained by multiplying
the relative % of each type of WBC by the total WBC.
The results you shared are all in the reference range,
except for the "large unclassified cells (LUC)".
These represent 2% of your total WBC.  They are
possibly large lymphocytes reflecting normal response
to a viral infection, for example, it's impossible to
tell with the data given.  But the rest of your WBC
info looks fine, so more than likely the LUC are not

Poikilocytosis:  this refers to a variation in shape
of your RBCs, in this case, mild, and no shapes that
were predominant or striking (non-specific).  This is
usually interpreted by looking at the blood smear and
evaluating the RBCs.  Based on that alone, I would not
be concerned.