Couldn't figure out why I have 400-500 leftover after all my expenses recently?? And what to do with it?

I've been back tracking. I've been looking at all my expenses!

I usually have a fixed amount I send for savings investments. A fixed amounts for all my bills. Fixed amount I budget for travel and lunch. And misc I budget.

After I made sure all the big and fixed sums left my account. I literally have 400-500 left!?!?

I did some calculations and it's partly due to

• not going to work means I save on travel and lunch money... So approximately the days off I had this month equate to saving 200

• travel and lunch money expenses has decreased dramatically in past few months. I have a cheaper route.

• I also don't eat as much as before at work and don't spend like10-15 a day anymore. Even when I do go in to work.

• I got a mini payrise so I was expecting to have 100-200 left over but not 400-500

what I really think has helped

• I've been fasting for many months. Not good but that's helped me pay some debt.
• imagine in one work day I'll spend £1 on chocolate, £5on meal deal, £1 crisps, £1 biscuit £4 drink =12
• sometimes £1 biscuit £1 chocolate £5 sandwich £5costa £1 cold drink = 13 Sometime I get a meal deal which doesn't fill me up and then a toasties sandwich from costa.. 13*20-23days = £ 260
• finding enjoyment and not spending boredom for food helps alottttttt

Now I notice I paid extra to debt this month and all my usual expenses deducted and I reduced mu costs overall. I have money to spend. I don't usually splurge on myself and feeling so happy. I feel like I want tot treat myself gift someone. Maybe send a small portion to savings but I really heavily save and obsess with that generally that I want to do something . Fun