H->HMS conversion HP-15C vs. HP42S vs HP67

[Siegfried]

Trying to check an Excel spreadsheet I tried to calculate 80% of 183 hours 38 minutes using Emulators of HP calcs on my iPhone.

using 183.38 ->H .8 x ->H.MS (via the Convert menu on the HP42S)

Legendary 67 and Free42 return 146:44:24, the same as Excel, while
HP-15C returns 146:54:56

I haven't had a chance to check on real hardware but was under the impression that all these emulators used real ROMs.

Will check on real hardware, but in the meantime, any ideas why the HP-15C might be different?