Rt-Ax86u RAM won't release after use of USB storage?

[Keiraija]

My router is RT-AX86u (fw 386), lately I just plug a USB 3.0 to use as a storage device on my LAN network.
But I notice that if I don't download from the usb, the RAM will always stay around 550/1024. But if I start to download from the USB, RAM usage will pump up to 990/1024 and will leave around 30mb free RAM.
Problem is: after the download is complete, RAM usage will also stay around 990/1024 instead of lowering down. Is this a normal behavior? Or RAM should be released?
The RAM will only go back to ~550/1024 after reboot of router. Hope someone can clarify this.
Thanks in advance!

 

[L&LD]

RAM will be used as needed. And released if needed.

Unless you're having issues, there is no need to worry about it.