Is there a better way to import stock levels than the way I'm using?

Hello,

I'm currently using SAP 8.82 and I'm using the OITW template to import counts into my warehouses. I am then going to Inventory Transactions > Inventory Posting and selecting the warehouse I imported and pressing OK. After a while it shows me what the count is and allows me to reconcile. The trouble is that we have hundreds of thousands of item codes, so it takes a really long time before I can get to that point and it has timed out a few times as well. (It's taking 30-40 mins at minimum and I've had it crash on me twice.

Am I going about this the wrong way, do I just have too many item codes? Is there a way I can do this quicker? We need to zero out the quantities for items that didn't get counted and get the counts into inventory for the ones that we did.

Thank you,