Her spendings will easily be 300k if she spends what she wants to spend. She is currently declaring 20k per month (240k per year) and that is without childcare that she would hire (another 40k) and rich girl schools (50k each, but school costs are usually excluded from support and split between parents) and she would probably spend a lot more on shit if she had unlimited money as before (let's say another 20k, probably a lot more, but I'm being kind). She probably thought she was kind by asking for 300k.
Her lawyers btw keep claiming on every financial declaration they made that they believe Ioan earns 100k per month, which he has only ever done once in the past 10 years probably. She is clearly still aiming to get 300k/year, but you don't get far with fantasy numbers.
Edit: I was pretty shocked when I read how much Ioan was earning with Liar, The Reunion and Harrow. It seems he was earning over 100k/episode. For non-streaming that is well above what I thought was his league (for comparison Tom Ellis in Lucifer and Matthew Rhys in The Americans earned less per episode from what was rumoured, Rhys earned as much in Perry Mason after he had already won an Emmy), and even now his role in Bad Boys for only being a two weeks shot was very well paid (160k) especially considering the movies moderate budget. Truly, it's insane that they had still so much on the mortgage left even if it was just a single income household. The wasteful spending must have been insane.