Cannot allocate more than 10GB of HTML5 persistent storage

Question

When I try to execute

navigator.webkitPersistentStorage.requestQuota(1024 * 1024 * 1024 * 15, function (bytes) {
        console.log('Successfuly allocated ' + bytes + ' bytes of persistant storage.');
        }, function (e) {
            console.log('Failed to allocate persistant storage!');
        });

then Chrome will allocate only 10737418240 bytes which is exactly 10GB, but I asked for 15GB. Of course, I did click "allow" to allocate more storage. Has anybody met this problem?

EDIT: I don't see any reason why somebody has downvoted my question. The reason why I want to allocate that much data, is that our application must store large amount of medical images. 10GB is definitely not enough. Furthermore, from https://developer.chrome.com/apps/offline_storage#persistent:

Maximum storage space -- As large as the available space on the hard drive. It has no fixed pool of storage.

EDIT2: NO, my disk is not full. Available space is around ~110GB.

Answer 1

I have reported bug to Google. Turns out that max persistent storage quota is indeed 10GB, but documentation saying "As large as the available space on the hard drive" is incorrect.

https://bugs.chromium.org/p/chromium/issues/detail?id=540574&q=persistent%20storage&colspec=ID%20Pri%20M%20Stars%20ReleaseBlock%20Component%20Status%20Owner%20Summary%20OS%20Modified