`root@OpenWrt:~# opkg update
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/targets/brcm63xx/generic/packages/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/targets/brcm63xx/generic/packages/Packages.gz
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/base/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/base/Packages.gz
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/luci/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/luci/Packages.gz
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/packages/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/packages/Packages.gz
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/routing/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/routing/Packages.gz
Downloading http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/telephony/Packages.gz
*** Failed to download the package list from http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/telephony/Packages.gz
Collected errors:
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/targets/brcm63xx/generic/packages/Packages.gz, wget returned -1.
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/base/Packages.gz, wget returned -1.
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/luci/Packages.gz, wget returned -1.
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/packages/Packages.gz, wget returned -1.
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/routing/Packages.gz, wget returned -1.
* xsystem: wget: vfork: Out of memory.
* opkg_download: Failed to download http://downloads.openwrt.org/releases/18.06.0-rc1/packages/mips_mips32/telephony/Packages.gz, wget returned -1.
root@OpenWrt:~# `
A package manager is a complex piece of software, the complexity raises with the number of packages and their interdependencies. Your figures only show the amount of free RAM before you invoke a RAM hungry (relative to the amount of free RAM you can offer) application.