Need help understanding string gauges

I have a concert Uke and the only brand my local GC carries is Martin. So, I purchased a set of M600 Soprano/Concert strings and put them on. Sheesh, they feel way too thin. The sizes are 1st .48MM, 2nd .65MM, 3rd 86MM, 4th 55MM.

Is this the normal size for a concert Uke? My 50 year old Harmony soprano uke has larger strings. Can someone help me out and tell me what size strings I need? I like tension........not floppy.

Any help is appreciated very much.

The M600 are fluorocarbon strings and they are usually thinner gauged (0191 0256 0340 0216) compared to nylon strings such as D'Addario (026 032 036 028). If you prefer the thicker diameter string, the D'Addario J92 Concert strings or Aquila would be a better choice.