Question for the electrically minded

[Dodgy Bob]

So this doesnt directly relate to the 306 as such, but I do use it in the 306.

I've got a old TomTom One N14644, battery is goosed and I really am a cheapskate, it still does the job so why bother getting a new one if this could be fixed for under a tenner. I've watched some youtube videos and got it stripped down and the battery out.

So the question is what does the 920mAH mean and does it matter?

I've only found one battery that matches all numbers directly on ebay but it looks dodgy and from china, but I've a fair few similar batteries with the right connection that look better quality and in uk but have higher mAh numbers.
So if i get one of them and put it all back together am I gona blow the device, melt the battery, or blow it once I put it on charge?

Battery that came out says:

Type: VF2
Cell: MAXELL 553443
Capacity: 920mAh
P/N: AHL03710503

Thanks in advance for any help.