The section for expenses used specifically for the work space only is for things that you paid for that you ONLY used for employment, and that your employer required you pay for (and didn't reimburse you). These are usually things like equipment or supplies (printer ink), but might include maintenance costs in some cases.
Something like AC costs or batteries for the smoke alarm aren't claimable because you would have those costs even if you didn't work from home. Also your terms of employment don't usually specify that you need these things.
