Sharleen,
The attestation paper was a legal contract between the military authorities in and those who chose to join up for a short period of time, usually 3, 6 or 12 months with the option, if need demanded and they were suitable, to re-attest for further service. The Imperial Yeomanry in the UK completed attestation papers and I think the other colonial troops sometimes did too but the bulk of the attestation papers were completed by people in South Africa who joined one or more of the hundreds of units that were created during the war.
Imperial troops in established regiments eg the Royal Artillery, Devonshire Regiment etc did not complete attestation papers. They signed service papers instead.
The attestation paper was completed when people attested for service. The top section contained biographical details and their signature, or an X if they could not write. There was usually a space at the bottom to record information on the date of discharge, character and address details.
Mostly the forms are of a standard design and mostly single sided. There are some examples here:
angloboerwar.com/forum/11-research/28903...-african-units#64255
. Some units chose to create their own forms.
From your description, it certainly sounds like you have your GGFs form. I would not worry too much about the age discrepancy. I have been researching men who served at Wepener recently and, as they moved from unit to unit, have had the opportunity to review multiple attestation papers for the same man. Usually, the age is consistently recorded (whether it is accurate I cannot determine) but, in some cases, there can be differences, in one case up to 10 years difference. I would imagine that when signing people up there was not too much focus on the accuracy of all the information recorded. The signature, length of service and pay rate was the important information.
Hope that helps
David