How many left

[Dieselman]

In the UK there were three trim levels, Base, S and SE.

Engines could be 2.0 Carburettor, 2.0 Injection, 2.1 Turbodiesel, 3.0 V6

Very few carburettor Xm were sold and it was soon deleted from the range, but a Base carb version had no suffix.
Base petrol injection was known as 2.0 injection, so "I".
Mid range was S for petrol, or SD for diesel.
Upper trim level was SE for petrol, or SED for diesel.

I'm sure you've worked out the the figures given in this thread are for UK Xm, but at the going rate it won't be too much longer before there are as many in the USA, as in the UK.
There are now more SM (99) and even GS/A (103), on the road in the UK than there are XM (91). The XM is now the most rare, series production, hydro-pneumatic Citroen on the road.