[ubuntu_studio] Kernel Upgrade is 52 MB in size - is this Correct?

50MB is about right for a keel upgrade. Usually there are multiple packages to be upgraded simultaneously when you get a keel upgrade. 3.13 is one of the keels available for Ubuntu 14.04. Those ruing Ubuntu 16.04 are on keel 4.4. You typically stay with one keel version the entire life of your Ubuntu release, although you get upgrades for bugs and security patches.

Currently you have not installed a version of linux-image-3.13.0-87-lowlatency. You've installed a version of linux-image-3.13.0-86-lowlatency, which is a different package. In contrast to most other upgrades, most keel upgrades come in the form of a new package. This is done so that the old version is not automatically removed, to keep that as a backup to keep the computer bootable in case the new keel doesn't work.