How might i show a change from 60 days worth of inventory to 30 days worth...

In computing the Inventory of January 2012, the Balance Inventory of previous two months (i,e 60 days), being November and December have also been included.

The way, the current computation is being made:

Particulars	Nov-11	Dec-11	Jan-12	Feb-12
Opening Stock (current opening is previous periods closing)	0	14.4	34.5	45.1
(+) Purchases	14.4	15.9	24.5	48.4
(+) Direct Labour and other Manuf costs	0	4.9	5.4	8.3
(-) Cost of Goods Sold	0	0	19.3	21.3
Closing Stock	14.4	34.5	45.1	80.5

The requirement now is to consider a 30 day base (i.e one month of previous inventory only)
Therefore, the way the computation should be is as follows:

	Particulars	Nov-11	Dec-11	Jan-12	Feb-12	Mar-12	Apr-12	May-12	Jun-12	Jul-12	Aug-12	Sep-12	Oct-12	Nov-12	Dec-12
(i)	Opening Stock (current opening is previous periods closing)	0	14.4	20.8	29.9	56.7	92.9	122.7	122.6	70.7
(ii)	(+) Purchases	14.4	15.9	24.5	48.4	76.4	96.7	89.7	47.2	27.7	24.5	19.4	15.2	18.7	19.9
(iii)	(+) Direct Labour and other Manuf costs	0	4.9	5.4	8.3	16.5	26	32.9	30.5	16	9.4	8.3	6.6	5.2	6.4
(iv)	(-) Cost of Goods Sold (first utilised from opening stock)	0	0	19.3	21.3	32.8	64.9	102.3	129.6	120.2	63.2	37.1	32.8	26	20.4
	Closing Stock (only current months unused can be carried forward)	14.4	20.8	29.9	56.7	92.9	122.7	122.6	70.7	-5.8	-29.3	-9.4	-11.0	-2.1	5.9
			[ (ii)+ (iii) ]	[ (ii)+ (iii) ]	[ (ii)+ (iii) ]	[ (ii)+ (iii) ]	[ (ii)+ (iii) ]	[ (ii)+ (iii) ]	[ (i) + (ii)+ (iii)-(iv) ]	[ (i) + (ii)+ (iii)-(iv) ]	[ (ii)+ (iii)-(iv) ]	[ (ii)+ (iii)-(iv) ]	[ (ii)+ (iii)-(iv) ]	[ (ii)+ (iii)-(iv) ]	[ (ii)+ (iii)-(iv) ]
									Note 1	Note 2	Note 3	Note 3	Note 3	Note 3
	Wastage		14.4	1.5	8.6	23.9	28.0	20.4	0
			[ (i)-(iv) ]	[ (i)-(iv) ]	[ (i)-(iv) ]	[ (i)-(iv) ]	[ (i)-(iv) ]	[ (i)-(iv) ]
	Note 1: Entire opening stock carried forward from May '12 is required to be used to meet the current months demand
	Note 2: Entire opening stock carried forward from June '12 is required to be used to meet the current months demand
	Note 3: As previous months closing inventory was negative, there is no opening stock in the current month
	Therefore, from the above computation it is clear that, in case if only a 30 day inventory holding is considered, the purchases in the months of July to Nov will have to be increased.
	Further, There will be wastage of inventory through the months of Jan to May
	The final Closing Inventory as of December of only 5.4 as compared to 44.3 when the 60 days computation was adopted.